Tirion is neutral. Horde did the same amount of questing with him from classic wow. Even when he was on duty, he wasn't in the Alliance we know of today. The fact he's human is all that people can go on. Race shouldn't automatically make someone Horde or Alliance.
Brann is pretty much neutral too. He shows up for an Alliance quest because it's related to his brothers. Otherwise the Horde interact with him just about the same.
Arthas was never part of today's Alliance. Same point of 'human doesn't equal Alliance' comment goes here. Rhonin too to some extent though he did convert to being neutral full time with the Kirin Tor leadership.
Jaina was the only character I could find from your list ( unless I missed a post ) that is now 100% Alliance. She did try to extend some kind of diplomacy with Thrall. Years ago I wrote about her and the neutrally issue but that simply isn't the case anymore.
The Horde have the same quest line pretty much in Grizzly Hills? With that one chick you save and help her sister, yeah? I can't recall Grizzly Hills being too different when I went through as Horde. I don't recall much of WOTLK being so different save for the starter quests and Wrathgate. Wrathgate was the biggest Horde/Alliance attention given in the expac. The rest was focused purely on an equal scale of fighting against the Scourge.
We might have had cool heroes. No doubt. They're now mostly dead, neutral, or both. Jaina honestly is a rare one in this day and age of Warcraft lore.