Think about it - What is the Thalmor's goal? To unmake creation. Aside from the puppet states, how many people are against that? Everybody and their God.
The Dominion's military power was shown in the Great War - a war in which they took the Empire by surprise and fed off of the chaos and damage of the Oblivion Crisis and Umbriel. Even then, nobody seemed to realize the Thalmor's ideals, and saw it as the Dominion just overstepping their bounds.
Things may be made a bit more clear when the next war rolls around. Great. Let's define the bounds of power here:
Aldmeri Dominion:
Alinor Armies
Valenwood Armies
Elsweyr Armies
Maormer (possible?)
Imga
Everyone else:
Cyrodill Armies
Skyrim Armies
Hammerfell Armies
High Rock Armies
Morrowind Armies
Orc Hordes
Argonia Armies
The Psijic Order
The Dragonborn
The HoonDing
Talos
Vivec (maybe? If he's still alive)
See the problem here? The Dominion is either royally outclassed, or they have something up their sleeve. Are they going to pull Numidium 2.0 out of thin air, or what? Bethesda is hyping them up to some great threat but.... it really doesn't seem to be true. They're not going to be able to fulfill their goals as long as they have opposition. That opposition is a concrete wall.
Thoughts?