I was 2 boxing this with a 44 brd/shd with 2 tank mercs. Put the 2 emblems in the "give" trade box, turned it in with the first char and Defan aggro'ed instantly on turn in, didn't get to turn in the second emblem. Both chars got credited with the kill but the second char was 0/1 on the emblem turn in step, so had to wait about an hour before killing him again.
Wanted to stick the 3 tanks on defan while bard lighted the torches but I never succeeded into actually opening the trade box on a torch. Just ended up killing him and killing all the bats/rats after. They are "greater undead bats/rats", the rats are lvl 32 and the bats 29 so they can only chip at you, not too bad.
I'd say it was easy, I don't think anyone fell under 50% hp.