You don't need cross server que. The only reason the the pool for rated wz is small is because the larger experienced PvP guilds have rofl stomped the casual teams. If they introduce brackets or something to that effect more people will play and be able to gain experience.
Even if they did add brackets or a better matchmaking system you're probably going to still have 2-4 teams queuing at best which means either all teams will end up facing each other or you will face the same team over, and over, and over, and over again which gets pretty stale pretty fast.
They need to add incentives to do ranked.