Looks good fun. Whilst there does seem quite a lot going on 2 things will happen when the bosses reach live.
1.) Boss Mods will help make tracking things easier
2.) People will learn what they need to pay attention too and what they don't. There will be things which don't matter to your role so that'll bring the list of stuff to watch out for down a bit.
I do enjoy fights with lots going on, and its about time they had a council fight with all 4 bosses active at the same time.
correct me if im wrong, but i seem to recall that according to the dungeon journal the Dark energy doesn't disappear before gara'jal posseses the boss again, causing a raid wipe.
Also i'm really thrilled by this encounter, it seems very overtuned currently, but im hoping they do not turn that down too much. Also, i shiver to think of what the heroic version would be like.