The Grotesque Dybbuk is on one of your Level 9 missions or is a Level 9 monster? If so, you should not be having such issues. Are you trying to rush and take on more than one at a time? I do recall that there were occasionally monsters that I had to defeat that I needed to be careful to take on at full strength and only 1 at a time. Is your build and gear consistent with similar PUs? What Faction are you? If you are Free Knights, I could help you beat it. When are you normally on? If you are RG, hopefully someone from that Faction will answer you here.