He is entitled to roll need on it just like you are. He participated in the same duty and put in as much effort as anyone else, and for all you know he has been farming this for a very very long time.

I farmed the battlemage robe for like 4 months or more, and only dropped for me post 2.1. However at the beginning of every run I explained that I wanted it and we agreed on either needing or greeding the robe.

Maybe you should have done the same because you could never guess what another person of the same class really has in mind for the loot.