3 stacks and was fine.
Just need to have someone who knows the fight step up and tell people what to do and it's pretty simple that way. Each person with beam I told them in say each time if they didn't move and they did it correctly. Put a marker on myself and had people stack on me for Eye Sore phase, first times people didn't understand it, but explained it and people were fine after.
Killed it with ease once people saw the fight, and half the raid hadn't seen it at all prior.