What about "Endgame?" We saw the Borg lose one of thier transwarp hubs and the destruction of Unimatrix One complex at least from the Borg Queen assimilating Admiral Janeway's neurolytic pathogen.
We're not sure what the effect of the destruction of Unimatrix One had on the Borg anyway, so it's kind of moot. That's like asking what the state of the Dominion as a whole was after their defeat in the AQ.
But regarding transwarp, we've seen Borg ships travel at transwarp independently. Lore's ship created its own conduits, and Seven (unsuccessfully) tried to install transwarp drive onto Voyager several times, showing that Borg don't necessarily need hubs. In addition to that, Voyager used a Borg Sphere's transwarp drive to cut their trip short. The cube from Q Who might have had transwarp, as the cube reached Federation space a full year faster than anyone expected in Best of Both Worlds, well after the Enterprise saw a cube outrun their fastest speeds.
I'm guessing that while transwarp itself is fast, the transwarp hubs make travel much more efficient and speedy (travelling anywhere in the galaxy in mere minutes) than standard transwarp, which could take any amount of time. And, again, the slowest transwarp speeds are still several times faster than warp.
Did the Dominion really defeat the AQ? Without the fleet from the WH, they still could have obliterated the AQ attack force with what they had... What'd they say, at least 40% of the remaining AQ ships- Victory would taste as bitter as defeat?