Admittedly, I wasn't using Dominion ships, I was fielding my new Borg Sphere for the first time against one of Pete's new Species 8472 Bioships. Also, Pete had over-stacked his ship with a couple of inappropriate upgrades to match my points value. But a win is a win and I'm taking it.
As for the Borg, I think they've been designed for bigger games as some of their abilities are really quite scary and I'm pretty sure that my fully loaded Borg Sphere could probably give a fleet including all six of my Dominion ships a run for their money. The lateral movement of the Sphere is also very powerful.
Giddy with victory I then played a scenario game with my Dominion ships against Wes' Klingons in which I had to protect four orbital platforms against a fleet twice the size of mine. Four turns later, the game was over. Normal service had been resumed... :(