Hello,
i noticed that most NPC´s who fight for you dont despawn when you die, so you could pull a lot of Mobs (even Elite), die and they will kill them for you. For Example Tyrael in ACT III Step 5 (after the first Quest). Works with most other NPC i have tested too, this one is just the best, because he hits hard and there are alot of Champion Packs.
HF