I was having so much trouble farming mobs for the Challenge of the Gods event, I decided to make a map of my own tuned to that. There are other maps out there, but each has problems -- I think this one solves the "need to be at half health" issue in an innovative way.
Still in the Review tab, but give it a try and see if it improves your chances to get challenge gifts. I manage two-three gifts per run. I still haven't managed to get the cloak, so... back in again until I get it.