Can I please get your opinion guys on Gruul´s Lair? We made 30pulls. Everyone have DBM. 15yards splits. 20k+ raid dps. We are dying like roaches. How is it possible? I know its possible to few people die on shatter and yes it happens but few things are 100% bugged. He should not be kicking main tank. That is bugged 123%. Second thing. Some people say that shatter is affected by totems, pets , etc....your experience? Tips for how to kill this bad boy here on server appreciated also. Good luck and have fun ingame.
He's definitely over-tuned compared to retail, but still isn't a very hard boss. He used to be easier (and tuned correctly imo) when armor mitigated the shatter damage. I think his health is higher than it was on retail. Possibly a tuning measure from back when the shatter damage was easier to deal with. The Shatter range is also too large here (maybe this is your problem). You can tell because you still take damage from people who are outside DBMs range finder, which worked perfectly on retail. But here, you can still take damage here when nobody is in range of you.
This encounter is currently suffering from a fundamental problem of a lot of fights on Warmane. They tune a bugged fight to be the correct difficulty for players, but then if they ever fix the bugs, it becomes much too hard and they don't change anything else to compensate for the difficulty increase. Other fights suffering from this problem are Illidari Council, Al'ar, Hydross, and Lurker.
I'd like to help more but you haven't explained what is actually killing you. Pugs kill him every day so he's far from impossible.