I struggle enough with Sienna on low difficulties, would hate for it to be harder! Got the Pyromancer subclass unlocked last night and not sure whether I prefer it over the starter one...
Currently only played Sienna and the dwarf - who I really enjoy. Need to try out the other characters this week.
Stick with her and level her up, use pyro class with beam staff with critical mass legendary trait and dagger then she is an absolute beast DPS. The snipe ability on the beam staff (hold rightclick then left click) is amazing for sniping specials and damaging down bosses.
After several days of derpy elves it's swayed my belief, from them strafing behind me while i'm stationary and then unloading arrows into my non moving head, to calling health and potions for them and them just ignoring everything. Or running far enough ahead so no-one can help them within 5 seconds if they get jumped and falling off the river crossings on halescourge...Yea it's been a bad few days

, also when you get to 25 if you are still having overheat issues there is a talent at level 25 that vents all overheat when you press your special F ability.