At the moment I'm seeing 2 other players on horde, and 5 on alliance. You risk losing some people down the line if the balance gets much worse, and the people who put the time in to make horde characters can't get enough to field teams, or if they can, the alliance is so established and able to support each other gearing up, that horde have no chance to compete on even terms.
Faction imbalance could well kill off regular queues for F2P twinks, leaving you with no-one to fight on horde besides 24s and newbies. That's not as bad as what happened to EU 49s, but worth thinking about.
To help boost the numbers of characters available to play on horde side, how about a little rule along the lines of:
'Players who roll more than one character on the most represented faction, will not be able to choose which of those characters they play in war games, until they have an opposite faction character made that they are willing to play too.
Instead they will play the least represented/popular class they have.'
They'd still be free to join regular BGs on whatever they want, and roll alliance first if they want, but if people aren't willing to support the bracket as a whole by themselves, maybe a little encouragement is needed.
They may not be doing it to the same extent, but anyone making alliance only, because the gear is better/the faction is better represented, is thinking along the same lines as people making 24s.
What you do for an advantage now, may well have negative consequences later on.