I could see the Borg winning a lot of battles, but I could see the Dominion being so ruthless, ramming ships, blowing up whatever they could using whatever dirty weapons they could find, like a virus mentioned above, and win the war in the end...
The Borg were mentioned in Scorpion having millions of ships.
I think the Dominion would essentially be overrun by the Borg regardless of how you put it.
Besides, it's the Borg we're talking about ... eventually they will adapt and keep coming.
Voyager Borg would also wipe the floor with the Dominion.
Voyager was lucky most of the time in their encounters with the Borg, but they never defeated one of their large ships with brute force.
The Interceptor in 'Dark Frontier' was an even match for Voyager which was eventually destroyed by beaming a torpedo on-board and detonating from inside.
Same thing happened with the Sphere which was supposed to take Icheb.
The crew never stood a chance with brute force alone and so they beamed a torpedo to a smaller ship which detonated inside the Sphere heavily damaging it in the process (but not destroying it).
From my perspective, the only time when Voyager was turned into an 'uber' ship was in Endgame.
Also, must we really remind ourselves the Borg were continuously defeated by TNG crew?