Flame On. Basically, what you have to do is to tank him beside the gates and have an extended stand opposite him. There'll be a rush, so every player who is not fixated will be shifted out. Those who are fixated should make them blow personal cooldowns (but should exclude deterrence/immunities). They should use external cooldowns on the first fixated players. That would mean that players will stay longer and will die at the end if it's needed.
More Like Wrecked-us. You should kill Tectus in Highmaul. To do that you have to destroy eight Motes of Tectus one after another (you'll have only 10 seconds between them) on Normal difficulty or higher.
Hurry up! Maggot. When the fight begins around the room the maggots start spawning. Some of them even spawn in the shallow water. The player of ranged should go and attack them (or if the damage is high, using 3rd tank can be necessary). To defeat them you should stand them in cleave of the boss. Personal achievement - one of the ways to do it is to go to the end, there you'll see a lot of moss. Use a cooled flamethrower to pop a draenic swiftness potion. After that, you'll need to receive from 11 to 16 stacks (you can get them at any point of the fight).
Be Quick or Be Dead. This will be more difficult than always. The stacks will go higher and will stay alive more doing their mechanics. Even better armor won't help that much.
Ashes, Ashes... The ashes will appear during the 3rd fight stage. As they fall past the platform's edge, there is a real need to have a player who have jump or teleport skills — only then it'll be possible to gather the ashes as the ordinary players will fall down. Your task here is to gather as many as you would be able, so demonic teleport, disengage, leap of faith, rocket jump or wild charge can help you here. Your creativity will be really helpful here. It's quite clear that the more players with such spells the better for you.