A lot of spells you can dodge or outrun. Dueling is a LOT of anticipation and reflexes. Even in 1.09, you could get killed before getting close to a caster (i.e. walking thru a frozen orb). You gotta learn to skirt the edges.

Synergies have also improved casters, but they're not unbeatable. What DOES hurt is the lack of life leech. If you fuck up once, you won't make a comeback, as you aren't getting any life if you manage to hit them. Basically, it's "do or die" against casters now.