I'm sorry if this has already been covered, but what is the priority of Powercast?
For the Mage, Psionic, and Alchemist, with their abundant offensive spells, it seems obvious. For the Priest, it's questionable. The Priest gets Lightning, Whirlwind, Falling Stars, and Make Wounds as his/her offensive spells.
I built my Priest in my MDP to be a caster, maximizing Intelligence, Piety, Speed, and Senses first. Strength, Vitality, and Dexterity were ignored, because these are stats more suited to melee and ranged characters.
Basically, I may have gimped my Priest, because his stats are 57/58/57 Strength/Vitality/Dexterity.
However, upon reflection, I realized that the Priest suffers from the same malus as the other casters, as they will never be as good as even a Bard or Gadgeteer at melee or ranged combat. Casters have to be level 50 to unlock the 3rd attack per round.

So, what's the question here?

I actually once had a Lord with Powercast, but that was mainly because I started him as a Priest, then changed him later after realizing that he didn't get the Dual Wield skill. (I went STR/INT with him.)

I really think the Priest should have had the Bard/Gadgeteer fighting values for a couple reasons:
* It would make there be a good reason to take a Priest over a Bishop
* In the earlier Wizardry games, Priests got accuracy (but not extra attacks) at the same rate as fighter-types. (It's also interesting to note that in Wizardry Gaiden 3/4, Priests *start* with a second attack, something that even Fighters don't get.)

I applaud the creators of W8 for that, as even though their franchise was collapsing, they still managed to get out W8, and balance out the characters in time to be bankrupt.
The Priest, just like the Bishop and the other casters, are slated to cast magic primarily, and deal physical damage secondarily. That's why they get poor numbers in the amount of swings and attacks.
This is why I tend to maximize what they are good at, dealing magic damage. Hence, Intelligence, Piety, Speed, and Senses should be maxed for a serious caster. Strength, Vitality, and Dexterity are more suited to physical damage dealers.