Ah I see
If I were you, I'd go with ice spells as your main source of damage, that'll slow enemies. My friend MEGARICK used to solo with a hydra sorcerer, but he's all rusty now.
I thought of going up to ACT3 to get an ice element mercenary like how I always do instead, so that I can focus on lightning and fire spells.
For me, the hardest to build up would be sorceresses and paladins.
I remember one time when I had my brother [age 12] play D2. He plays MMORPGs. He quit playing until ACT4 before he fought Diablo saying it's very difficult, while we solo that game. What a wuss.