The Alliance playerbase FIRMLY established, with their 2 years of complaining in Cata, that Thrall was always a Horde character.
Therefore, Khadgar is Alliance, for the same reason. And Magni. Illidan is iffy, in fact I’d give a pass on him since he was fighting against the NE’s in Frozen Throne.
Velen is absolutely not iffy, though. At least when Thrall was neutral, you couldn’t go kill him in Orgrimmar. You’ve always been able to kill Velen, he’s a full-fledge, flagged-for-pvp faction leader.
Alleria also makes little sense. One moment she’s strolling around the Vindicaar with Vereesa, talking about how much she hates the Horde, and half a minute later I’m doing quests with her. WTH?