Citation needed. While we know they were on the losing side of the Great War, we know the Blades won enough minor victories that the Thalmor still consider them a threat. We also know that the Blades no longer had a direct line to the Emperor, as the Mede Dynasty replaced them with the Penitus Oculatus, so they were fighting with a handicap. And on top of that the area protected by the Blades got hit by more in the way of disasters (succession crisis right after the Oblivion Crisis, Umbriel, the fall of Baar Dau and the Red Year) than the Thalmor prior to the Great War.
No indication whatsoever that their loss was due to bad information.
While that is not untrue:
He knew enough about the Thalmor's plans to hurt them and to avoid them when most of the rest of the Blades' organization was killed.He was not a field agent, but is now believed to have been behind some of the most damaging operations carried out by the Blades during the pre-war years, including the Falinesti Incident and the breach of the Blue River Prison.
Eh? He knew Alduin was going to come back before he came back, which was why everyone thought Esbern was crazy.
...which is the Thalmor to the T.
As I believe has been pointed out before, if you're letting your enemies get into your inner sanctum just to mislead them, that's not cleverness that's incompetence, and the Thalmor aren't that.
Also, they had the location of Esbern written down as well, and that is perfectly verifiable.