FTFY
It's getting worse as we gear up. Nothing's living long enough for SMN multi-DoTs to breathe long enough in high DPS groups, you'll be lucky if SMN even does 1/3 the damage of BLM on a Bennu before it's dead. Now it's just burn burn burn everything. Not only that but the current farm meta IMO is about pushing phases faster and faster, skipping mechanics, and SMN will never win there.
SMN's so good on paper but if you personally use SMN and use BLM in the same gear, same group, the difference just jumps at you. You'll notice halfway through the fight you're multiple % behind and possibly getting a mechanic you should have skipped, or scenarios where adds get burned down with BLM that suddenly with SMN it's surviving longer and the OT is eating more damage, taking away healer attention from DPS or healing the MT.
I do think, if there's a proper buff, SMN will win T11 and T13 (well, win in the sense that it will win on Bahamut, not necessarily the add phase, but that's irrelevant to any good group these days). Honestly don't think SMN will ever compete with BLM T10 and T12, the multi-DoTing gets less effective every week, and T10 phase pushes are very annoying as SMN since the DoTs stop ticking.