Phase 1
Phase 1 lasts until the first Hellfire and is pretty simple if you are positioned as stated above. The players stacked will have to deal with a set of eruptions. To do this they must run directly south and then a little to the east, taking care not to go near the healer who has the pulsating debuff.
Shortly after Ifrit will spawn 4 Infernal Nails and the DPS players must kill them before Ifrit jumps for Hellfire. This is a DPS check. It's quite easy in this phase but there are two more of these. You should be aware that during the nail phase Ifrit will use a single Eruption on the off-tank and ensure it does not hit you while you are DPSing the nails.
Groups will typically kill these nails in a clockwise order to avoid multiple nails being killed at the same time. When a nail is killed it will use a small arena-wide AoE but this damage can add up. After the nails die or if you were too slow Ifrit will use Hellfire. If you were successful heal up and get back into position.
Phase 2
About 5 seconds after Hellfire Ifrit will cover almost the entire arena in plumes. The safe spot is in front of Ifrit to the right. Shortly after this Ifrit will then jump into position for his Crimson Cyclone attacks. To dodge there you should line up next to the Ifrit clone that dashes off first. You should then move up the arena wall until the last clone dashes. Then get back into position. The healer with the debuff can't stand with the group so they will have to dodge this from the opposite end of the arena by standing close to the final clone to dash.
During this phase the group will have two sets of eruptions to dodge followed by the second nail phase. This nail phase consists of 7 nails and is a DPS check just like the last one. Be aware of the single eruption during the nail phase and be alert for the new tether mechanic. This attaches a chain between the off-tank and a random DPS player. The longer this chain the less DPS the player does. If you are a ranged DPS player you will be close enough to the tank to not care, but a melee DPS player will have issues. The off-tank can either go near him/her or the melee DPS player can switch to one of the nails next to Ifrit.