@Shar.
Well first off, I have a strong feeling Swen will be doing the whole kickstarter thing with the next game. We can clearly see all the great changes that were added into the game in the past year from the extra $900k they got (10% of the mil went back into kickstarter fees

) I know my generosity will be increased a bit

I have a witch (Scarlett) and battle mage (Roderick). For witchcraft, I only found two spellbooks, one to summon an undead swordsman and that bloodletting that she already came with. I think in the full game witchcraft might become more useful.
I found a warrior in the tavern, but keeps turning into a huge grey rectangle so I don't enlist him or her. Not even sure of the gender the glitch is that bad. For a while it was fine, but then started to glitch again. There is a warlock in the mayors house on the 2nd floor. With a party of three I was able to finish all boss battles.
For monsters that are frozen or petrafied, I find uses the teleporation ability does massive damage, but everything else is weak when attacking them. I find those skills are useful to help reduce the amount of attacks your party is taking on for a few rounds then a way to kill an opponent.
Character setup:
Roderick mainly uses melee and fire spell damage, I have his fire set high enough to summon the fire elemental.
Scarlett is pretty much just a mage in the back of the party.
I have her summon both a wolf and undead swordsman. I didn't find many spell books for witchcraft.
Air +1 (teleport monsters away, does major damage when they are petrafied!)
Earth +2 Poison, Fortify, Summon wolf
Ice +2 Ice Shard, healing
Witchcraft +2 Summon undead (most useful summon)
Warlock - forget name. I have him use mainly ice, air and ice elemental summoning.