One very special person made a difference at Kvatch. And the battle had already been lost, and the main Daedra force had moved on. It is unknown if the Hero's presence would have made a difference in the actual battle. But again, he is the PC, and he is special.
Aldruhn had far more soldiers than Kvatch. And given the invasion, they wouldn't all be sitting around while the Nords are invading.
And I thought the Redoran won a pyrrhic victory at Ald'Ruhn. I could very well be wrong though.
Or as Lord Rugdumph gro-Shurgak would say, a phallic victory.
I'd say on Vvardenfell they did. Ald'Ruhn, Maar Gan and most of West Gash routed probably. Expect major grabbings by Hlaalu and Telvanni.
I doubt they'd try that at the time, considering that Redoran is the only thing standing between them and getting sacked by the Nords.