Questions like this one always come back to the key question about the MU: Why
are humans different? Where is the point of divergence?
If it's because the whole universe is different somehow, then all bets are off on how any given species is going to be. Raw speculation is fun, but that's all
we've got because there's no other basis to work with.
If it goes back to the precursor race being different, then that would affect the Vulcans, Romulans, Klingons, and Cardassians, too.
If it is just the humans, but they've always
been different, then there's no telling how far flung the effects of that would be, either, given that the Preservers put humans all over the place. And heck, for all we know, some nasty group of primitive MU humans stole a Preserver ship and wrecked havoc for a while.
If it is at some point in recorded history, it still begs the question of how many alien visitations and time travel encounters would have had different outcomes, and how much effect would that have? Think about Rasmussen
for a moment.... and that's just one example out of many.
The MU Dominion may be completely different because somebody who, in the regular universe, was a time traveller that went back from the 27th century and saved some ancient Vorta ancestor, was instead killed by a human or someone directly or indirectly affected by humans before they had the chance to in the MU.