Siriaktwo

*filtered* this guy. Stop talking about him. He's gone. Can't we just pretend he doesn't exist now?

I'm like 99% sure that you only need to do the highest possible difficulty. So if you do Heroic first, you don't get anything from doing Normal and LFR afterwards

Without knowing ANYTHING (obvs) I'd say that Vyranoth probably helps us defeat Fyrakk, likely sacrificing herself. That just leaves Iridikron who, most likely, will be the bridge into the next expansion - kinda like Gul'Dan was with WoD into Legion.