Notes:
Pretty much anything that can do damage :P as long as you can dodge anything will be fine. Easiest setup would probably be the 5 THM strat but if you don't have THM ranked you can just come whatever class you want as long as you don't drag your team down.

Our Party Setup:
GLA
CON
CON
DD/THM
DD/THM
DD/THM
DD/THM
DD/THM

-Tank goes in aggro then get hate on Ifrit
-One Con on left, one on the right
-Everyone else behind Ifrit - centered
-Attack as usual
Tips/hints:
-Ifrit always uses a TP move right after he dashes, so wait til he does it then do whatever you're gonna do

PHASE 1:
Tank goes in gets Ifrit, stays at assigned spot til phase 2.
DDs do damage as usual, try not to take hate from tank.
Mages try not to move so much, in this phase since ifrit does not do any TP during this phase.

PHASE 2:
Ifrit will starts phase2 with any TP. So as soon as you see it uses it's first tp, starting counting down you got 10-15 seconds between each TP.
-You have enough time to do about 2 to 3 actions.
-USE the spell/ability right after he does a TP. After you did your actions just wait til he does the next TP.
-Tank stays in the same spot, but still goes out to reposition after ifrit finishes dashing.
-During dashing, everyone(mages and dds) gather at tank.

PHASE3:
(Ifrit glowing and will do 3 continuous eruptions and 3 dashes)
-Same thing here, everyone gather at tank to rebuff..etc when he does dashes.

Phase4:
-Nails: all dds will follow the assigned leader dd, and only take one nail down. It will use eruptions during this time as well so be aware!
-It will only do one dash if it does. Sometimes it can skip dash and go straight into hellfire, so be ready.
-One THM do Sacred Prism + Sanguine Rite on party
-You don't really need sentinel anymore but it wouldn't hurt to use it anyways.

Phase5:
It's right after hellfire. In this phase, he does TP every 5-10 seconds.
-It will do 3 dashes that spawns 3 of them, tank should be at the same spot as in all the other previous phases, he/she should never change this spot, its very important.
-at this phase you will only have time to do 1 or 2 actions, I would stick with just 1 action to be safe, once you're more skillful you may stick 2 in there but for beginners you gotta do 1 action and then wait it out.
-Everyone must do it right after a tp, don't wait til 5 seconds you see the tp to do it because you will get hit by the next one.
-DDs only do 1 ws/1 ability in between TPs to be safe. don't try to be super DDs not til after you're skilled at dodging anyways but for safety reasons just stick with one action in between he's TPs.
-DDs/THM will finish him off in this phase.