Waited like a couple of hours with open MCH slot for o3s weekly kill(granted all other slots were open except casters), no MCH joined... Actually nobody joined so we just took bonus nin lol...
But pretty much if I get MCH in the party I expect subpar dps even lower than what I would except from a smn(despite me doing pretty ok-ish).
Also in pf I saw all kinds of parties for savages with slots open for everybody - smn\mch\blms\whatever without much "meta comp" memes.(EU data center).
What I see from fflogs about DPS shows that it's pretty much up to player skills. Every job can do around 4k which is enough to clear any Omega savages easily. Even like 3.7-3.8k should be enough.