Just wondering how other tanks are pulling this off. We have to go at a certain speed, or else we catch up to fire before it despawns. My issue is if I continuously move backwards around the edges of the room, non-stop, I'll hit the original fire that spawned the adds in P3.
So, I pause between the first shadowblazes, and then move the adds. Thing is, sometimes 1 add will clip the fire. It will kind of stop running, or stop and turn, and be hit by the shadowblaze.
So I tried strafing, but that showed my back and didn't end well (one of those duh moments, but had to try it).
In normal I just backup nonstop, and can reset them twice (but our dps is so good, Nef goes down as adds reset the first time).
Using stuns are absolutely a viable way of handling them. It's all a matter of timing and making sure you never stun them when they're in danger of having a shadowblaze thrown onto them.
Pause between shadowblazes, with about 2s left on the shadowblaze timer start moving and you'll be fine. Technically you can start moving a second later but this way you'll be completely safe. Don't panic, do it at this pace and you won't clip any old fires. The reason to play it safe is the Nef adds have some erratic behaviour where they can't properly hit moving targets, which has a chance to screw up the pathing. If that happens when you move late you're likely screwed.
Obviously stop as soon as you see the blaze on the floor to see where it'll land and you're a reasonable distance anyway. Most of all though stay calm.
I'm usually healing our paladin tank who's tanking the adds in phase 3, the way he does it is exactly as Mogias describes, just check the timer for shadowblaze, with 2 seconds left on it move the adds, be sure to cover enough distance so the fire doesn't creep back up to them and reset their energy, but don't move too much or you'll catch the previous fire at the end.
Backpedaling will not be fast enough once the shadowblazes start coming faster, due to this I would advice not to backpedal at all so you don't get used to it.
Be sure to rotate cooldowns for when the adds get high stacks and are about to "die", incidentally these times tend to line up for when we get electrocutes as well so it all works out with the cooldowns, even if they don't I've noticed that our tank is more often in the risk of dying from high-stacked adds than from the actual electrocute.
Stuns are good to give you a few seconds of breathing room but you'll have to learn when to do it without any chance of a fire reaching them while they are stunned or you'll be screwed, but it's very beneficial especially when they have high stacks.