I prefer PUG over MNK

Before we have WHM, stoneskin is the spell you need in order to move in front of Ifrit, seeing it doing a move that's not targeting you and unleash a front combo, without the risk of taking away half of your hp.
(in case the rear is cooling down or you simply want to look cool)

Simian Thrash + Stoneskin cancel on 3rd hit, you don't need to worry about jump and crack.
Used to have the need to cancel by pressing the button again.. but now you just need to hold a direction.
(In case Stoneskin is cooling down.. there's always Cure)

The only drawback is lacking some TP when compared to using a MNK, but preparing yourself whatever throwing weapons will allow you to store some TP even when the healers are too busy to take care of you, or when your hp just doesn't allow you to take the risk. Addition bonus, if you can react fast enough, there's a free hit whenever Ifrit jumps, before the target cursor disappears, while allowing you to move to the tank safely.

Anyways.. if you're playing in a party with a trustworthy healer who can take care of you,
MNK is more stable to the party as the damage dealing combos from the rear is good enough.
In the above front combo example, if you misjudged a crack targeting you and run to the tank,
your party will thank you for the quick finish.