Mage wasn't my first pick, since I tried it a bit during test period and it felt too weak. At least in single player. Fire magic works nicely if you have a melee tank friend, since it seems to deal nice area damage and mage can stay away from the trouble. Ice mage + melee tank combo could also work, since ice slows enemies down. But fire explosions just look much better!
However, then I got an idea to combine blood magic with elemental magic and immediately fell in love with Dead Raiser + Staff of Embers combo. Summon (one or) two skeletons who will follow you around and do the melee/archery stuff for you. Then just stay on the back row and spam elemental magic into the mix. Your skeletons won't take damage from your explosions. Tested this a bit in Plains, Black Forest and Swamp and it seemed to be fine even for solo player. Haven't tried it in more hectic combat situations (or in Mistlands) yet, though, but random enemy encounters are definitely doable.
Magic could be my new favorite?