However, SMN CAN hit the 50% cure potency cap, and if you're there INSTEAD of a WHM (which is the only time you'll be spamming cure 4s enough for enmity to be a problem), you can pop Allure atma for -enmity and +MND too. So now you're popping a 6-700hp cure4, with much less enmity from doing so, whilst supplementing this with Healing Ruby 2 or whispering wind.
I've duo'd several Abby NMs as THF with a SMN friend for support/occasional hate steals so I can pop sneak attack, or they run in so I can trick attack (for TH+ only). They never took hate and the avatar did probably as much damage as me from BP alone (it didn't melee because we didn't want to feed tp - so obviously neither did the smn).
For the record, he has lvl 90 whm too, but even as a Taru THF, I got by just fine with cure 4s. BPs sped the fight up a load though
I'm almost certain that at no point could he have turned around and said "This is like watching paint dry".
If you're there to help proc staff/club as well, and healing is already covered, sub war. You have the choice of war, whm, pld, mnk. War offers aggressor to help our sucky acc; berserk to add a little damage if you want to speed things up; defender if it's taking a while to proc and you want to deal as little damage as possible; double attack to get tp faster.
Yes SAM is a better sub for melee, but you lose the proc ws. WHM is better if extra healing is required. SCH or RDM are better if mp might be an issue, but again you lose procs.