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.