How high of a level did you get the Mage? Sorcerers are fucking
badass in this game, and it's probably the first game that I have ever played (across decades of gaming across essentially every format) that made me feel like an all powerful caster. Their gameplay does have a much spiker feel though. It's all wind up, huge payoff and then lots of downtime. Or you could just get away with charging staff shots, which gets pretty broken with Holy Boon. You also shouldn't have to worry that much about resistances or immunities if you are carrying three elements, or at least two and a non element like Miasma/Maelstrom.
That being said, IMO the funnest classes to play would be: Magick Archer (only end game Vanilla, and then all of BBI where they truly shine), Assassin and Sorcerer in that order.
This is playing an Assassin (or Strider):