you need masks to kill DT at 5 stacks or above...at 10 stacks he supposedly drops the amulet...the amulet is what is rumored to be used in the cave. also only the tanks need the mask
We've been progressing on DT at 5 stacks. As far as we can tell, the masks do absolutely nothing. We had people both with and without the masks, and they were getting hit for just as much. The only potential point where the mask might help (which we haven't tried yet) is negating the two consecutive 18k+ hits that the tank gets right after the swap.