In WOD we had a sticky with raid mechanics vs our defensives, which was super handy - I'm hoping someone will come around and do the same this time around (as I generally can't be bothered keeping a sticky up to date).
But to kick things off-
Nythendra: Cloak immunes damage but does not clear stacks of infested or stop you from acquiring new ones whilst cloak is active - so don't be like me and stand in bad with cloak on because you'll ramp up your infested stacks.
Cenarius: Cloak does not clear stacks of Creeping Nightmares but new ones are not applied whilst cloak is active.