Gotta dumb 'em down, don't ya know! Gotta revert to that old fantasy stereotype of humans being the balanced "chosen" race who's good at everything but not excessively great at any one thing while their non-human pals are each fundamentally incomplete embodiments of dangerously flawed extremes!
So anyone important in the Alliance who's not a human gets smacked with spontaneous crippling deficiencies so that the well-rounded homo sapiens can show them all how to get things done the right way.
He already schooled the worgen on their hunting turf. Now he shows the ten-thousand-year-old night elf army how to fight a war in the trees. Next he'll be showing the dwarves how to drink just the right way (wait, he already forced their current government upon a spontaneously mute and indifferent dwarf populace, didn't he?), and showing gnomes how to invent just the right way, and showing the draenei how to pray and fly the Exodar just the right way.
Then they can all celebrate by renaming their capitals after variations on the name "Stormwind" and replacing every banner with the gold lion on a blue field. Because the Alliance is all about many varied races coming together for the common cause of preserving their respective nations...by conforming to the standards of a singular dominant race because the rest are all fundamentally "broken" and in need of human leadership to not completely screw up at every turn.
You know, despite Stormwind consistently botching damned near everything they did for the entire time between the Third War and Varian's return. Yeah, those guys are totally on the ball and worthy of being the heart of the Alliance. I know when I look at the persistent Defias, Blackrock and gnoll threats in Stormwind's lands, my initial reaction is "hell yeah, the other races totally need that sort of stuff screwing their kingdoms up too."