RChu1982: Where the rub comes in, is hybrids:
Lord: I don't have experience with them, but their melee looks to be mediocre (they get a Dual Weapons skill bonus), but aren't hitting like the Fighter or Rogue. Valkyrie: This is my first time creating one, I'm going with Polearms, as that's her weapon skill bonus. They get the Divinity spellbook, so are not going to be casting that much offensively.
Ranger: Gets free Scouting, ranged crits, and Ranged Combat skill bonus. Ninja: Thrown crits, thrown auto-penetrate, Critical Strike. They get the Alchemy spellbook, so are somewhat balanced between offense and defense, while the Alchemy spellbook arguably gets the best level 6 and 7 spells (great even without Powercast).
Monk: I have no experience with this class, though some might (especially those that hire RFS-81). Apparently, they don't need much equipment, as they fight with Martial Arts skill (hands and feet). They get the Psionics spellbook, and have Stealth, so they are protected. There are many Psionics spells that work fine without Powercast, especially before Ascension Peak, where magic falls off.
Samurai: I have no experience with this class. Apparently, you are supposed to use a Sword with them, as that's their skill bonus (a Mook can use the Giant's Sword, though later in the game). From what I know, a "Lightning Strike" can occur, though that's unknown if it's Sword only, or Dual-Wielding. Knowing the Wizardry spellbook, without Powercast, can still allow them to cast buffs, or attack spells if the enemies are lower level.
Lord: I have used this class. In fact, my very first party I had a male priest who I changed into a lord later on. I don't really remember how well this build worked, but I distinctly remember getting Power Cast with him. (I happen to really like healing magic, and Power Cast + Heal All is the most powerful multi-target heal there is.) For general use, my recommendation is to plan on giving your lord the Diamond Eyes; before you get it, a Hammer makes a good weapon to equip in that slot, as it uses the same skill, boosts Mace & Flail (which affects your main weapon, if it's also a Mace/Flail), and II.does have a KO chance. Al alternative approach is to plan on using HP drain equipment with them. Lord tends to be a late bloomer due to the way Dual Wielding works.
Valkyrie: Unlike lord, which is more of a late bloomer, the Valkyrie is good even early in the game. By the time you reach Arnika, you likely already have an Awl Pike, and there's more spears, including the Lance, for sale there. Later on, you can buy Stun Rods and Dread Spears; that's plenty in terms of weapons, and while they may not be the strongest weapons in the game, they're readily available and still good enough for Ascension Peak and the Cosmic Circle. If Intelligence and Senses aren't both terrible, it may be worth boosting her Artifacts to 35 so that she can use the Amulet of Life; being able to both resist and treat the "dead" condition can certainly come in handy.
Monk: RFS-81 doesn't show everything the Monk is capable of, due to his inability to use magic. I've found that, even 4 levels behind, Psionic Blast is quite useful in the hands (brain?) of a monk.
Samurai: Apparently, Lightning Strike needs you to have physically attacked in the previous round. If you've done that, then Lightning Strike might trigger with each attack, adding 3 extra swings if it does so. (I don't know whether this is melee only.) This can give you a nice boost of damage, but (especially if you're using the Giant's Sword) could alos get you a not-so-nice loss of Stamina.