The thing is that Hraesvelgr hasn't ever attacked Ishgard in the lore. He and his brood aren't part of the Horde. They just mind their own business in the Forelands and in the Churning Mists. Hraesvelgr only leaves the Churning Mists to go hunting in the Forelands.

If the WoD is derplander I don't think the trailers will be truly representative or alternatively he could be from some type of alternate Eorzea. The Screenshot I mentioned had that grey 'Echo vision' look to it and he was in his WAR gear.