Having mained as a SMN for FCoB and played it throughout 2.3 onwards, I can say unequivocally that SMN's only struggle with FCoB and T8 (pre-nerf), in terms of mp issues. SMN will most likely never be on par (mp/ availability to AoE damage) with a BLM, so mass AoE dps isn't an issue (e.g. 4+ mobs -> spamming Blizzard II after DoT application), so the only major problem is long drawn out fights (i.e. FCoB and T8), which is where the problem became glaringly apparent.
I understand some people have issues with some of the newer dungeons being bothersome, but they're not something that Jobs are specifically based around, as all non-Coil encounters favour certain Job(s) over other in terms of ease and dps output for the fight. Take Levi (HM)/ (EX) for example, it's the perfect fight for a SMN, but you don't/didn't see other people complaining on the forums that these non-Coil instances are imbalanced, because it doesn't really matter.
In FCoB (and T8 when in mattered), you're expected to pull your weight, as much, if not more than other dps Jobs. When you're Job is gimped into not being able to pull off it's maximum potential because the fights mechanics/ in-buily Job mechanics hinder this, then you have a problem.
Getting back to the thread topic (more specifically), I hope (as you mentioned) that the development team is indeed looking into doing something "adjust the job before 3.0", however, as I can't find the article/ video with which Yoshi-P addressed this point, so I can't say much more, other than I remember them mentioning it would be around Heavensward time, which makes perfect sense (i.e. new Egi's > forced re-balance anway).
I know Yoshi-P and the dev. team are rather prescient and plan well in advance with FF14, but for some reason, the matter of SMNs (in general) and their dps/ mp in FCoB (or long, drawn out fights in general) hasn't been addressed properly on these forums by any representative (as far as I'm aware :/), nor has it been explicty been addressed in any LIVE letter/ producer letter.
I'll wait to see what happens come 3.0 anyway.