The difference between BLM/SAM and MCH, though, has nothing to do with anything inherent to pure DPS and everything simply to do with MCH being more dispensable. It's not Yoshida's job and its in a less popular role that already typically relies on the basic arbitrary composition requirements to be taken at all.
No part of that changes in adding a raidbuff. And if MCH is to remain too attention starved even to get simple potency buffs (i.e., what even healers can somehow afford), how the hell would it see time of day enough to get a raidbuff?
And again, there is no directly relevant increase except in terms of total contribution, which every decent state of balance has correlated tightly with.Also, on the 5% raid buff point, I was specifically referring to proportions. It means different things for different jobs depending on their personal vs. raid contribution. If NIN is doing 30k rDPS, 3k comes from buffs, so 90% is personal.
Except MCH has slipped into the highest total contribution among Physical Ranged a few different times now even since becoming purely physical, and Bard and MCH likewise saw periods of 2 to 3 major patches where one or the other was clearly superior even when they had identical portions of raid dps.From my experience with other things in this game, when SE mishandles something for this long, meaningful changes only come when there's a full design overhaul. I don't see why MCH would be an exception.
You're not going to fix overly slow or rough tuning by giving MCH a raidbuff. At best, it changes nothing for how often or well Physical Ranged get balanced, as we saw across Heavensward and Stormblood. More likely, it worsens issues in the short-term, as you've just added another and novel complicating factor, as per whenever one was added (as in Stormblood and Shadowbringers).
Tl;dr: The devs likely have even less "want" to spend the larger amount of time required to give MCH a raidbuff than to simply apply the necessary potency increases.