I was thinking that as bad as the White Gold Concordat was for the Empire, it may not have been any better for our gold-skinned Stormtroopers. We're mostly seeing it from the Imperial perspective where they lost Southern Hammerfell and had to ban the worship of Talos but it strikes me the Thalmor didn't really gain ANYTHING except that religious strike.
After all, the Emperor deeded them territory they couldn't successfully subdue let alone add to their Empire. Likewise, while the Thalmor have time to rebuild their military forces, so has the Empire. Even the Thalmor's persecution of Talos has only stirred up worship of the Hero-God in many places as matrydom is won't to do.
It's quite possible that the Thalmor are only posturing when they think the WGC was a big victory on their behalf as it gave away their best chance for victory against the Empire.