Wicked rodeo achievement help

Just wondering how we are supposed to pass this. By the time I get him under 20% the area is 50% covered with sandtraps , there are 3 waves going all the time and you have to kill 3 elementals to break his shield. All while he shoots projectiles at you that never miss. There is literally no way to survive this. Is there a way to get rid of the waves or traps?

I've manged to get through story achievements 1-6 and though some were very difficult they weren't like this, it seems impossible.

@Ozzio.8024 said:Just wondering how we are supposed to pass this.

Evade/dodge.