i think everyone will still use classes on ifrit and moogles, because they are mostly carebears. I can already see monk a must in moogle fight (hundred fists + fist of fire should bring down gladiator in phase 2 in a second, meaning way less trouble. And sap is much better of shadowbind until you have mp) but obliusly i can already see people ignoring jobs in the old primarl because they are used to that.
that said, bringing down all 4 nails on ifrit cut down the damage of hellfire like 1 nail + sentinel.