SMN vs BLM, I tried both of them in T10 and T11. Ended up staying on BLM both.
T10, I initially felt SMN would win but as noted by Seravi, MP is ridiculous. SMN is better for the adds, but not by much since ending a BLM rotation in Flare is about a roughly 10% DPS gain so BLM can do pretty well there - also, with a good group the DPS check isn't too demanding so you can go BLM and still do very well since you'll do more damage the rest of the fight. The movement isn't too bad, first phase you can skip Wild Charge stacking completely and just stay spread out. Last phase is bad though, you will have to move no way around it and you generally can't AM (or if you can it's harder to do since there are so many variables in a very quick situation). BLM does win T10 though without Ballad, that's for sure. During our progression I did have some saves by Manaward and Apocastasis, both legitimately useful. Those are conveniences SMN doesn't have, and as far as I can tell the pet does nothing for the mechanics.
T11, MP's also an issue for SMN. A big one. However, the mobility for BLM is also very rough ... still trying to get it down but in general you WILL have to dodge at least one part of each Nerve Gas, if not both (still working on trying to be able to AM to a for sure repositioned safe person but right now I just dodge it myself), and during adds you will have to move, but you can usually move with a proc or Swiftcast rather than just plain movement. Rough fight for caster no matter how you slice it, the only reason to bring caster over BRD or another melee is for the Cube's Physical Damage 50% reduction.
So far from what I've seen, and I'm not trying to be pessimistic, T10-13 are melee/BRD fights. SMN's MP issues break it as bad as T8 does, unless you're willingly giving Ballad for healers, and BLM so far, in my eyes, is in a proportionately worse spot to melee/BRD than it was in T6-9 since it's harder to pass off or ignore mechanics. You bring caster (from an optimizing standpoint, anyway) because you need caster LB or something specific like the Cube. 2.4: Dreams of Melee. It's not a big deal because you still bring a caster but I feel less important than I did back in other turns so far. Maybe in a few weeks I'll feel differently but that's my experience thus far.