The Dominion would clearly be defeated as an empire by the Borg. The Vorta and Jem'Hadar don't possess either the technology or the cleverness and independence of thought to be a match for the Borg. The Changelings would have to do the thinking for them, and I think they would rather hide from the Borg, instead.
In my view, the end result: the Founders send the Vorta and Jem'Hadar to their deaths or assimilation, and while using them as cannon fodder and a distraction, the Founders escape the Borg and remain undetectable by them.
In my view, the end result: the Founders send the Vorta and Jem'Hadar to their deaths or assimilation, and while using them as cannon fodder and a distraction, the Founders escape the Borg and remain undetectable by them.