I don't leave the Monastery until level 10 or 11, and the Psionic/Divine casters have 80-90 in their respective school. I use divine trap on the trapped box across the bridge. Knock can work to spam/grind, but it often sets off the trap.

This gives me 1 decent offensive spell (w/ some low level casting experience) each to ride out with.
Firebomb - Alchemist
Ego Whip - Psionic
Whirlwind - Priest
Iceball - Mage

When I play a solo bishop, I try to get 3 of the 4 above spells before leaving the Monastery.

This reminds me of how some Final Fantasy 7 player decided to reach level 99 (the cap in that game) before leaving the reactor (the very first area of the game). It took an unreasonable amount of time (I'm pretty sure more than enough to max out the in-game timer) and is not something I would suggest to anyone.

I've never seen such an issue; when raising INT to 100 at the fountain, I would get the message, and the Power Cast skill would be open.

I find that Piety's effect on SP is rather miniscule at higher levels, particularly when the character knows a lot of spells. (It seems that this particular term is a linear combination of Piety and spells known.) This is especially true for Bishops, who tend to learn a lot of spells from books.

For casters, I tend to do INT/SPD for more standard caster builds, or SPD/SEN if I'm not planning on keeping the character around the whole game (like when I create a mage but replace her with a gadgeteer later). (Why boost INT if the character isn't going to be sticking around long enough to get Power Cast?)

Piety to 100 for Iron Will because it's extremely helpful late game.
Even for (especially) fighters, I make Piety the third priority when playing on expert. Late game insanity can turn TPK real fast when a heavy hitter has several swings and attacks per turn. 4 swings against the party with a polearm (or giant's sword) can be a major problem.

Once the two primary combat attributes are 100 (or 80 in the case of senses), I start giving to piety. STR/VIT/Piety at 100 makes for a major tank.
I keep my fighters with low initiative so they act after enemies have walked within extended range.

--
Side note:
Have you run into an issue of not being willing to play the same party twice?

My first party (before I really understood the game) killed the Savant in 1 round of melee.

2 lords
Monk
Samurai
Mage
Ranger (never touched melee and I didn't know they could mix potions)

I'm at 95 Intelligence for all 4 casters, so no points wasted there. Once I get to Trynton, I will get the +5 for Powercast. I'm doing Speed now at 3 points per level up, as I think Snakespeed is very important for primary casters who protect as well. I alternate between 2 and 1 points(1.5 average)every level up for Piety and Senses, keeping them both even, because as DTGreene said, Piety's effect on SPs isn't too great. I seem to get more benefits from just increasing realm and spellbook skills, and of course picking the good spells that I now have access to.
The Bard and Gadgeteer have been my tanks, because Intelligence and Piety really don't help them too much. I already maxed Dexterity(Reflextion)for both of them, and their Strengths are in the 90s, hoping to get Powerstrike soon. I'm getting their Speed and Senses up as 3rd and 4th priorities, because who doesn't like high initiative characters with multiple swings and attacks?
Vi Domina and Myles, at this point, are completely useless to me(both at level 6). I just got my Bard and Gadgeteer to level 15, and my 4 casters are at level 14. There is no catching up for RPCs at this point. They will just steal my experience. I just recruited them for their quests, and I'm dismissing them safely(Vi at Heli's bar, Myles at the town entrance).
I have a few doings in town to do. I have this thing where every 2 or so NPCs I talk to, I make sure my Bard gets a point in Communication, because unless you cheese dialogue, there is ONE chance per NPC to get a skill up. Bards are the best choice for Communication, because they get a bonus to it. I also tend to grind that one Savant Orb at the Tower that drops the Holy Water spellbook. That is literally the only way to get it. I kill his friends, paralyze him, then run away and save. Then I can save/reload scum until I get the book to drop for my Priest. It doesn't take that many tries, in my experience.

Actually, there's another way, though I would expect most players to reject it; kill Lord Braffit. Lord Braffit, I believe, has the same drop list as that particular Savant Orb, including the small chance of dropping that Holy Water spellbook.

(If I do end up creating a mod, I will probably add the Holy Water spellbook to Lord Braffit's shop inventory, as well as to the T'Rang who sells low level Water and Air spells; perhaps it might also be appropriate for the shop in Trynton, even though it wouldn't be particularly useful there.)

It's really not that big of a deal. When I used to run Bishops, I would be religious about saving spell picks, so that would be a must(grinding Holy Water spellbook). That made the Bishop useless for the first half of the game, as she had to be carried until I saw Crock and Sadok and got their spellbooks.
Now that I'm doing "pure" casters working only one spellbook each, I can be more liberal about picking spells at level-up. It's just a luxury now to have Holy Water for my Priest. I think it's 36 or 37 spells for the pure casters to max out their spellbooks, easily attainable.
According to Flamestryke, there is around a 25% chance for the Orb to drop the Holy Water spelllbook. Much easier than grinding the Higardi Bandits for the Ariel's Slippers, Prospero's Cloak, and Mercucio's Blade.
And no, I won't be killing Lord Braffit for a level 2 spellbook :)

In recent playthroughs, I've taken to not allowing myself to save Bishop spell picks (or, more precisely, they may not be saved for spells that require higher class levels; saving one because her skills aren't high enough at level up time is acceptable. Also, it is this sort of thing that makes me glad that level ups can be saved instead of being forced immediately the way they are in games like Wizardry 6/7 and the majority of JRPGs).

In Wizardry 8, I pretty much always put exactly 1 bishop in the party. (Ideas for future playthroughs; Bishops can equip everything a Priest can, so how about having one that's focused on melee combat, or perhaps one that specializes in Artifacts?)

Yes, but it feels wrong that, unlike every other low level spell in the game, this spell and Mind Stab are not available in spell book form. (Mind Stab I would add to Anna's shop list.)

Then again, I would get rid of the SP regen on the Infinity Helm, because that again feels wrong, given that the helm isn't usable by pure casters and it provides more SP regen than anything they can equip. It also feels wrong that, in the long run, Fairies end up with worse SP regen than other races.

I can't post again. I must have exceeded my post limit/character limit. Anyways, this kind of goes back to Humans and their balanced nature, and the fact that they have no negatives, and the most attribute points.

Here's the logic for giving humans the most attribute points:
* There's the obvious issue that humans don't have any racial resistance bonuses (though at least they have no *penalties*, and that, at least, is significant).
* The other is that games where you allocate attribute points tend to reward specialization; often a character's power is related to their *highest* stat, not the average stat. If you want a specific expert skill, the fastest way to get it is to use a race that starts with a high value in that stat. Also, other benefits of stats, the Strength bonus to damage being the obvious one I can think of, are benefits you may want to focus on. In any case, games like this tend to reward specialization. Humans don't have this benefit of specialization, so it makes sense to give them a higher stat sum to counter-balance this flaw.

By the way, humans were terrible in earlier Wizardry games; they suffered from low Piety, and their other stats were just average. So, not only do they not benefit from specialization, but they have a significant weakness, and their stat sum is lower (which also makes it harder for them to qualify for advanced classes).

(This weakness applies to Wizardry 1-3 and 5 (not 4, as that game is *very* different from the rest of the series), as well as some of the Japanese spin-offs (Wizardry Gaiden 1 and 2, for example; WG3 starts borrowing some of the additions of Wizardry 6, and in doing so acquires some of its balance issues plus some of its own (Lizardmen being overpowered, for exmaple).)

W8 was my first Wizardry back in 2001. It's so well balanced and addictive that I can't go back to earlier Wizardries(I've seen Youtube videos) due to the lower quality-of-life technology.
I agree with you about specialization. Which is why I took Humans to take full advantage of the maximum total stat points. I am putting the maximum points, both on creation and on level-ups, into 2 attributes, then keeping the next 2 equal. The last 3 attributes are at base(and they're at least 45). So by level 29 or 30 I will have 4 attributes maxed and 4 expert skills. Then the last 3 attributes will get 2 points each. So both balance and specialization.

By level 29 or 30, I will likely have already beaten the game and either started a new one or (more likely) switched to playing an entirely different game.

Unlike Wizardry 1-7 (again, excluding 4, as that game is *really* unusual and unique), XP requirements continue to increase exponentially no matter how high your level increases (aside from an integer overflow that first happens around level 50), so reaching really high levels is a pain. This isn't Wizardry 1 where a level 200+ Bishop (attainable via glitch in the Apple 2 version, or by actually garning those 100 million XP normally) takes the same amount of XP to level as a level 13 Bishop.

I find that grinding is a normal part of the game. I always whack Crock, Milano Calzone, and Don Barlone, as those are nasty characters. Crock is a kidnapper, and he has a good treasure chest in his room. Don and Milano are unwelcome guests that stole the Sixth Bough from the Trynnies. Plus, I honorably pay the Don for the Astral Dominae, and he still sends his goons in to intimidate me after I get enough artifacts. I'm good to everybody else. I don't shoplift from them or pickpocket them. I'm not running a party of scoundrels.
In order to be comfortable with Nessie, and Don Barlone, and the Rapax areas, and Bayjin, I try to grind in the Swamp and the Mountain wilderness(there's good experience to be had there). I find that you can get into your level 30s+ before getting to Ascension Peak. That's just me though. Play how you like.

Sounds like you might enjoy Wizardry 1. (Just don't use the identify glitch on the Apple 2 version to quickly reach level 200+.)

Or, perhaps you might look into Dragon Wariior 1 on the NES. (Not the remakes, as they *significantly* increased the XP and GP rewards from enemies.)

I enjoy grinding, to an extent. It seems richly rewarding to fight enemies that give experience, gold, items, and skill ups. My party is all level 15, having completely cleaned Arnika out(well, the set treasure chests, set items, and set monsters.) Monsters seem to have 3 spawn points randomly: The Savant Tower and Airport(various Savant machines), as well as near the crashed ship(various Higardi thieves, the strongest being level 10 Higardi Brigand, which are pretty tough.)
My Bard is starting to shine now that I gave her the Bloodlust and a Heater Shield. She can still use her instruments to buff the party with the Angel's Tongue and do damage at range with her Piercing Pipes. So losing her ranged option doesn't seem to be too much of a loss when the Bloodlust can hit 3X per swing and I think 2X per round(I pumped her Strength and Dexterity.)
The Gadgeteer made herself a Tripleshot Crossbow, and she uses the Diamond Epee for melee along with a Heater Shield. She uses the Lightning Rod occasionally, though it's starting to not be very good against the level 17 Savant Berserkers.
The casters are all pumping Speed for Snakespeed(they're all at 99 Speed, so close). They have 6 realms being developed except the Alchemist, who doesn't get Mental Magic. Once I stop grinding Arnika, I will make a beeline for Trynton for that +5 Intelligence and Powercast.
I have to sleep scum for Antone to give me the best weapons and armor, as well as Braffit and He'li to give me enough Magic Nectars to be able to regenerate mana, as well as buy the spellbooks from Braffit and Anna. So hanging around Arnika for level ups isn't too hard to swallow. I'm getting level 17 Savant Berserkers spawning, which give decent experience.

One thing I observed many years ago, but which isn't actually that useful to know because multi-classing is rather terrible in this game, is that, if an Alchemist happens to have a Mental Magic spell (from a previous class, for example), they will still be able to raise the Mental Magic skill as an Alchemist.

Another, related, observation: If a skill increases enough without a level-up, it is possible for the character to gain access to a new realm with a spellbook, but to still not be able to improve that skill; I believe this will fix itself at the next level up.