If there's a next time, they should do something more radical like have the Dominion reinforced by the Daleks during the Dominion War.
I think the Daleks are a good match for the Jem Hadar though their agenda would be to create a Founder Dalek.
Cybermen Borg team up is too obvious and even then it doesn't really work without tweaking them to accept each other which the Borg would never have done. I read the Cybermen can't even convert non humans which makes their conversion of Trek aliens like the Deltans and Cogen V inhabitants a oversight unless there's to be a massive twist like the Borg overriding the CyberBorg.