Not sure why nobody reported this one, though I do tend to believe bug reports are pointless at this stage of things. But anyway…
Beginning sometime around the patch that kicked off the anniversary event, the Lurker in the NY raid gained a new bug. If you DPS too much in the first phase you will come back to him for the start of phase 2 and he will take no damage. He will perform all of his attacks and scripts as normal, but his health will never move. Once again, we’re all being penalized for being too good at the game. The list of encounters that bug out when you do too much DPS is absurd and are probably actually in the majority now.
The point at which this bug triggers appears to be around 67-68% health give or take. If you can get the lurker below this number in phase 1 he will be bugged. This is a pretty trivial thing to accomplish and you can actually push him significantly lower than this with a group of max gear and highly skilled players.