You're understating it by a mile. Of course its primarily damage, but the difference when it comes to tougher mobs is what separates the jobs so much. The problem is MNK is nowhere near as good on the big stuff, where as SAM is nearly or just as good on the things MNK is good/great at. Further, the applications of a SAM on HNM are beyond what a MNK is capable of while still defending itself and doing damage, because its defensive ability is native. So instead of going /NIN to everything, it can pick between /WAR & /THF to maximize its already good DOT or burst damage, respectively.
BLU suffers the same problem when it comes to SAM, frankly, but it's even worse, since it isn't as good at merit and it has the same form of attack as a SAM in HNM situations, Burst damage. BLU can do well and can defend itself very well, but SAM is still stronger on the whole.
Er...For the record, I never said BLM shouldn't get anything, just that it doesn't really need anything. What I actually mean is that it shouldn't get anything to expand its horizons, just something that would improve what it already does, i.e. Magic Damage. Comet, Meteor, & Ultima would be alright.
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