Mm yeah, the Dominion is 20 years ahead of the Federation in terms of technology yet it just seems way too weak in FO.
Not quite!

The Dominion ships were only superior before the federation could counter the Poleron technology. Now they are much like the Klingons, offensive oriented and per unit of mass, able to out-gun the federation.
I don't see the weakness with the dominion, I mean the Breen BB is the strongest Battleship, the V-13 is capable. The Defender is an amazing addition to any fleet! That beam burns.
The problem with the Dominion AI is...none of you have played against Baron. He whooped my bum bum. He's insane with the dominion.
But the thing about the Dominion, is unless they can get established, they are weaker than the other races. Much like Canon, their supply lines are weak. But if they can get established, with several moons and supply mining, they can indefinitely out-produce any one else.