I have just determined that I can get one of my character's average AC up as high as 32 with the items I have. (Without the *Light* *Shield*, I could probably manage 24 AC with a different shield. Doesn't that seem a bit high?

Of note, some of the items contributing to this are:
Cloak of Stealth: +3 AC, +20 Stealth for 2 more AC
Fey Ring: +4 AC, +20 Stealth for 2 more AC
(Notice: That's 11 AC from accessories alone; another Fey Ring would give another 6 AC, but would mean that she wouldn't have positive stamina regen (Robes of Rejuvenation are +2, and she can't use the Infinity Helm because of her class.)
Amulet of Healing: +3 AC (total of 14 from accessories)
*Light* *Shield*: +10 AC (I think this item is too powerful, so I don't use it)
High speed gives her another +2 AC.
That's 26 base AC already. Doesn't that seem rather high? (Remember, this is *base* AC, not *average* AC, which is going to be higher.)
Factor in armor, and we could get 32 AC on this character, and that's with the Cap of Wiles (helmet with -4 AC).

Not to mention, 40(!) Stealth, which could be 60 with another Fey Ring, or 65 if you add a Lithe Buckler. Consider that this character doesn't even have Stealth as a class skill!

Now, can you guess this character's class?

(One more clue: Her main weapon is the Vampire Chain.)

Not bad for a Bishop
(items left only Bis or Pri, and the latter is pretty redundant with a 4 school Bis)
but it also shows that she has neglected speed, else refletion might add inn,
also there is a shield bonus that increases with shield skill, its max is based on the shields ac bonus.

Armourplate at PL7 will add 4 more,
(all that together is probably not even close to what you need for Brombadeg in Qusaris Reforged Mod;)
but the combination of Guardian Angel & Body Of Stone is sometimes more effective than high AC.
If you add a razor cloak in, you can bring down foes with AC higher than your best attack value in party.

The character is indeed a Bishop. (Notice the Cap of Wiles; that item isn't particularly useful on a Priest because of the lack of high level Priest Mental spells, but it allows a level 24 Bishop to reliably cast Mind Flay/Cerebral Hemorrhage/Concussion at power 7.)

Actually, it's Dexterity that she neglected, as that's the skill that provides Reflextion. She actually has 125 Speed, and having 100+ Speed (or is it 90+) gives you 2 AC.

Of note, 75 Power Cast seems to give about a 20% bonus to spell power. At 76 Power Cast, Superman boosts stats by 42, and Haste grants 84 (!) Speed to the party (tested in fake combat).

Also, Priests do have some advantages over Bishops:
1. Lower stat requirements. This makes Power Strike easier to obtain (Dwarf Priest can get it at level 11; Bishops can't learn it until much later.)
2. Faster leveling: Bishops need 33.333...% more XP than Priests, putting them potentially 2 levels behind at higher levels. This allows Priests to learn higher level spells sooner.
3. Priests get a 25% bonus to Divinity. This lets them learn spells more easily, and it also eventually allows a level 24+ Priest to reliably cast level 7 spells spells at Power Level 7 (including Restoration and Death Wish).
4. Priests get more HP per level. At 50 VIT (which is lower than the Priest's minimum requirement), Priests get 10 HP every 2 levels, while Bishops get only 8. (Of note, Alchemists get 9, Psionics 7, Mages 6, and Fighters I believe 18.)
5. Priests get the Pray for Miracle ability that I always forget to use.

So no, I don't think Priests are redundant.

Do note that, at least when it comes to Restoration, Power Cast seems to give a bigger boost than the 7th Power Level (compared to PL6).

What you point out for the Priest is exactly one of the reasons why beginners are usually recommended to start with a Fighter, Thief, Priest, Mage, Alchemist, and Psionic. Gives you the basic hard hitting power, a sneaky shadow dweller/lockpick/pickpocket, as well as the most power form of each of the 4 main spellcasters. Only when you know more how to actually use these abilities should you start messing with more advanced classes.

Of course, in earlier iterations of the series, it was easier to do that, since when you changed profession, you reset your experience as well as your stats, equipment capabilities, and casting power. At least with 8 it doesn't take so long to start building a very powerful character without profession changes.