The Dunmer in TES:O aren't part of the Dominion and even so politically wise the Dunmer great house and council system is still more stable and advanced then any political system the humans had.
Which is a major point because nowadays Nords treat mages as social pariahs unless they are the court mages another thing is that the Nords of the 4th era show no qualities of being like the 500 companions, despite what you think mages are a very powerful source especially going after an enemy that practices magic as a cultural way of life, magic isn't "for the weak" or "for the elves" it's a very powerful and useful thing for armies. The Nords nowadays don't have mages in their army and then don't have a crazy powerful enchanter that helped them enchant a ton of the gear as previously stated by Hevnoraak another thing is that by far a frozen wasteland where life was extremely harsh provided more hardened soldiers then what skyrim has.