Pets help a little, but what shines in my eyes is locust swarm, which allows you to really run around and watch as ennemies die, and sometimes it can clear an entire room without you even needing to enter it.
Dire bats is also an amazing spell, being both great as an AoE spell and for single-target
I really love WD, and if I go HC i'll do it with one
I don't know if any other class has a skill the likes of spirit vessel. I think it's amazing
One might frown at "blood ritual", but 15% mana used as life is really not much. At lvl 46 my health pool is 16k life, so the 1% increase in health regeneration far more than compensates for the 15% cost of a 160 mana spell.