viable build when partying with caster

Hello all,
I am new to this game. I play with my brother who is a caster (either ranger or witch) and it seems that all things die before I get to them. Granted, we are only level 12 ATM. Does the mechanics change with increasing levels? Due to the apparent lack of being able to respect (back to ground zero), makes me wonder if I should pursue a "caster type" build or wait for game mechanics to kick in with more challenging mobs. Thanks in advance for your thoughts.