I found that hero mage/DK warrior worked really well. Elemental missile with a lot of points in every element kicks an almost obscene amount of damage, and with none of the initiative problems an archer has.
Some creatures are immune to one element - none are immune to all four. You will need a lot of Mana potions to play a mage, but they are easy to get.
I won the game without too many problems using this combo, so for that reason I would recommend it <img src="/ubbthreads/images/graemlins/smile.gif" alt="" />
