Why does everyone seem to skip over the last sentence of that dossier?
Because it's an easy way to vilify Ulfric and his goal of liberating Skyrim from an Empire that capitulated to the Dominion, despite it being a boldfaced lie?
And because nobody seems to understand the meaning of "Asset" in spy language. The Aldmeri Dominion considers Ulfric an asset because his war is essentially diverting resources in the Imperial empire. On top of that, the Empire loses valuable manpower during the war, further weakening their armed forces.
It's brillant really. High elves are very patient people, given their long lifespans, and so they can stave off war a few decades and watch men kill off each other while they provide subtle manipulations that push them in that direction. The lie they planted in Ulfric's head to make him feel guilty in order nudge him in the direction of wanting to prove himself. The secret kidnapping and torture of Talos worshippers. Hell, it wouldn't surprise me if the Thalmor pay people to spread rumors about it to get the Nords riled up.
In the end, a Stormcloak victory is best as it allows a potential alliance of Nords and Redguards in the future, from my perspective. Redguards, having freed themselves from the Thalmor, will look at the Nords as kindred warriors as both races honor strength and prowess in battle. A nord-redguard alliance with great warriors and masters of the way of the Voice is the worst kind of army the Aldmeri Dominion would have to face.
Couple that with the fact there are probably rebel groups within the Dominion itself (think of the Aldmeri Dominion as High Elf Nazis), primarily composed of Khajiit and Bosmer, who are essentially second-class citizens in the Dominion, and you have a perfect storm for the downfall of their Third Reich (ironically, it is the third Aldmeri Dominion in Tamriel's history).