As Raze said..it seems somewhat biased toward magic, Having played all 3 main classes i would rate them as follows 1. Mage, 2. Ranger and 3. Warrior these were all played without using any priest class skills at all. I played my very first character with summoned creatures and realized very soon that my skillpoints could have been used more wisely in my main skills rather than in uncontrollable summoned creatures. Having said that, put together a creature with a Mage head and wow its literally a BLAST lol Ive tried the ranger head and it takes too long for its SINGLE spell to recast and a warrior head just didnt seem to benefit me nearly as well as the mage head.
I have also found that its more efficient to spend points in 3 or 4 main skills and not spraed points out and have alot of mediocre powered skills...of course magic based skills NEED (mana efficiency) and (destruction) maxed at 5....lockpick at 5.... i had +2 wiz necklace...and carried the +1wiz bow on my mage for more experience.
There are many combinations but i felt the Mage is the most powerfull and the Ranger is awesome too once it gets Explosive Arrows built up!
All the classes can be powerfull if you dont spread the skillpoints all over the board!!!!!