Very good, now someone gets it.
It's not that the dissedants are upset with the Dominion, they just do not like the Thalmor.
As I said before, with the way the provinces are set, taking out the Thalmor would be an easier job than the entire Dominion.
Now if you take out the Thalmor, what does that leave you? Well, for starters the Elswyer Confederacy might become sovereign again because they credit the Thalmor for bringing back the moons. Now though the Thalmor took over Valenwood, becoming part of the Dominion has helped many of it's citizens and being an actual Mer race, even if you took out the Thalmor (which would be preferable to quite a few citizens), the citizens would still want the Dominion. Neither Altmer or Bosmer want to be under the rule of Man again. So at the present time, putting up with the Thalmor (as much as they are disliked) is a more favorable option than being part of the Man-run Empire. The only reason why they are part of the Empire was because of a huge machinization that no longer exists. The Elves has been waiting a long time for the right time to secede and make a Nation of their own.
Just saying, if a direct naval assault is anyone's primary means of getting onto the island of Alinor, you're doomed unless you spend a couple generations building up a formidiable fleet and then manning it with capable sailors because the Dominion, notably the Altmer, have a navy that is rivaled by none. It is not invicible by any means, but you would seriously need a much larger fleet plus better trained sailors. Considering the experience of their sailors due to their age, they almost have the upper hand no matter what training a group of Men have.