Wouldn’t necessarily balance any particular zone. And you’d still have varying distribution of players within a zone.
There’s no way to provide 100% balance, without forced queuing and enforced 50/50 in a subzone - and that is not World PvP, it’s a set of bgs within a zone. Plus… even within that queued 50/50 subzone, a % of players would still afk or run away.
It’s not a simple thing at all, zone sharding is least worst option. If they can improve it awesome. But works better than any alternatives to sharding I’ve seen suggested.