Wintergrasp is a mess of a joke of a failure. Every time Blizz has tried to fix things, it hasn't been a major fix.
The easy solutions:
1) Make Wintergrasp an instanced zone. This would make it unconnected it to the main zone/continent servers, and therefore reduce the MASSIVE lag on both ends when Wintergrasp is active.
2) Make defense possible. So far (at least on Dark Iron) defense has been largely a futile effort. For the first 5 minutes or so of a fight, yeah defense can put the hurt on offense, but after that it largely becomes an effort in pointlessness while waiting for the offense to break through the door to the vault. Speaking of which...
3) Remove the Vault of Archavon. WHY WHY WHY WHY WHY? I won't lie, of course I have taken advantage of the vault, but it's ridiculous that a "raid" boss that has no tough-to-deal-with abilities drops tier 7. I understand that Blizzard wants to make this more accessible to the casual gamer, but this is overkill. Naxxramas and Obsidian Sanctum already do that job capably, we don't need an even easier boss dropping equivalent gear, or especially not pvp gear.
Did I miss anything? Let me know.