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.
You can find a vendor for witchcraft spellbooks on the top floor of the tavern (the same vendor also sells the rogue skillbooks).
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.
Anything with crushing damage will do great (like this crushing fist skill from way of the warrior).
Oh... duh lmao! Yeh I had him in my party. He sometimes freaks out like Arhu unexpectedly and starts attacking my party. This mostly happens if a trap is set off causing burning damage.
Yeah, this friendly fire reaction is way too easy to trigger. Typically, i set the ground on fire, the fight ends, one of my guys runs over the fire, gets a bit angry, runs over the fire some more and is now angry enough to attack me. I think environmental damage shouldn't trigger this reaction, at all.