It's Lit!

In case it isn't clear, this achievement cannot be soloed.

This one is pretty straightforward, and in gear should be an absolute breeze.

Every time the boss hits 100 energy she casts Soulrend, spawning an add from every player in your group except your tank. These move towards her and do some raid damage if they hit her. For the achievement, one player needs to stand next to each of the 4 brazier in the corners of the room. Once your add spawns the brazier should be lit AF. Everyone should just then kill their own add, then go help the healer with theirs, while the boss stays near the middle to give more time for each adds. Our ~295 Ilvl DPS had no problem killing their own adds in time, so you shouldn't have to worry about them getting in.

Only other thing worth mentioning is that it appears the flames go out after a certain amount of time (30+ seconds, past that can't be more specific) so you want to get her low before you light the braziers. We overdid this a little and had her at about 20k health when the adds spawned, so we just killed her and ignored the adds and still got the achieve no problem.

My btag is FrostyShot#1667 if you have any questions about the metas. (US Servers)

Since I'm one who often doesn't have access to many people to do achis, thought I'd answer a question I had before doing this: it's doable in 4 people, doesn't require 5, at least without having anyone in tank spec, it spawned adds from everyone.