After you group up all the mobs you need to cast Demoralizing shout 7-8 times before you start spamming aoe, your casters will pull aggro when mobs reach 20% hp but should not die. If you have issue with pulling aggro and dying wait a bit more with hellfire or use a lower rank.

Once your warrior gets geared and gets reflect damage items and buffs it becomes a lot less stresful.

The question is do you want to funnel your gold into your warrior or do you want to run around with 4 mages and oneshot people