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.
I haven't seen that episode in a long time but what about that Sphere that pursued Voyager into the transwarp conduit, didn't it avoid the pathogen?
Those conduits confused me when I saw them in Endgame. If they had one that exited in or just outside the Sol system why didn't they send the Borg Cube through there instead? Why give Starfleet days of advanced warning for them to assembly a fleet to intercept the vessel? Starfleet could only field a dozen ships in Endgame to face the Borg threat. A Borg cube would have cut through like a hot knife through butter and before anyone can really do anything everyone would be doing assimilation two-step on Earth.
Add to the fact that Starfleet then just let Voyager approach Earth. If I just saw a ship exit from an exploding Borg vessel I'd have ordered the ship to power down, boarded her and taken the ship and crew into quarantine. But this is TV, you need to have a nice happy ending with Voyager nearing Earth.