Messed around with PUG a bit on Ifrit.

Fists of Earth does increase your autoattack damage quite a bit, but MP draining at 30 MP per punch means that you cannot sustain it for very long. I think it's best to auto attack without the buffs until 3k TP, then turn on Fists of Earth and do your combos. Turn it off to regain TP as your recast timers cool down.

Howling fist damage was around 550 with Fists of Earth up. Simian thrust totals around 400. Other WS do around 150.