Going to mention some things about tanking on PGL since there's already a lot of good and helpful information about DPS'ing the fight.

I've tanked this countless times on GLA, MRD and PGL and for me, PGL is hands down the most fun tank for this fight and works extremely well as long as you have competent healers that can dodge eruptions.

The DPS alone can can match and even surpass any of the individual THMs if you know what you're doing. With that plus all of the enmity gaining skills, you will have so much hate that the THMs can go to town on Ifrit without having to worry about getting his attention. Which makes for some seriously quick runs.

If you're familiar with tanking then you should know the basic stuff. Keep Taunt, Provoke, Flash on CD. Evading when he's in triples doesn't seem possible from what I've seen. That's debatable, I just haven't seen myself evade during that time personally. Parry however does work during triples so Foresight is another skill you can also keep on CD. The turning trick when he lands from Dash is especially more useful for PGL since this class takes more damage. If you don't know how to do it, there is a rock near where you normally stand to tank. Just be at it when he lands from Dash and wait for him to turn, then run back to the regular spot. You avoid swipes and Incinerates with this technique. Combo'ing is a bit tricky. For those who don't know, you can activate combos in the the required position and run back to your regular tanking position before animation even goes off, which is very useful for this fight especially if you have other melee in the PT so you don't turn Ifrit and have them eating Incinerates or swipes. Timing is what you need here, I would suggest waiting when Ifrit does a TP move (anything except Vulcan Burst since this will knock you far out if you're at it's back/side) before chaining combos. So when he does, you just have run to his back/side to activate Pounce/Concussive Blow and immediately run back to his front before your animation goes off. It may seem like a long run to his back but really you only need to go a little ways back but still be underneath him. Play with it until you find the sweet spot. Stack Blindside + Blood for Blood(optional, I don't use it when tanking just because I don't like having another source of losing HP) and you'll be knocking out 600+ damage on Howling Fist. Once you having the timing down, you can start timing your combos in between swipes also which will raise your DPS. I also like to keep Fist of Earth off until after Hellfire. It's a more crucial time to have it on and it's good to have the defense buff and the added DPS to push the fight to the end.

Gearwise, you could go with HP melded stuff and some Mythril Wristlets for added defence, but to be honest, if your mages can't stay alive to keep you alive then gear isn't going to help you. The fight is so short that CNJ will never run out of MP (they really shouldn't regardless of who's tanking). Personally, I wear my STR gear with Mythril Wrislets and do fine with it.

If you're PGL main and haven't tanked this fight, I highly recommend it. Hell, I recommend it to anyone with Lv50 PGL. This fight alone made me a huge fan of PGL. It's just so fun running around constantly and firing off combos whenever the hell I want and watching the the huge light show for Simian Thrash will put a smile on anyones face. Hope this information helps and happy hunting!