Free Server Transfers (FST) are causing unexpected terrible problems. There are no safety or security features put in place to prevent a server from becoming lopsided. If a server has a healthy 50/50 population, that is great! If a server is 60x/40y favoring faction X, then Y might be inclined to leave. So Y transfers off and now it is 70x/30y favoring X. Does blizzard care at all in maintaining server balance? Or do they only care about shortening the server size for queues that might be 1-5 minutes? I think Blizzard over exaggerated about queue times becoming a concern. Only the couple biggest servers had that problem, and because of other factors, the server sorted itself out anyway.
The problem you will have is once a server slips from 60/40 to 70/30, it has ripple effects to 80/20 or worse. This causes people to quit and unsubscribe. Now your original concern of lowering the population from 20k to a point of no queue is irrelevant. Thousands upon thousands of people have quit because what you should have done is only let the faction with more people transfer off. No one wants an unbalanced server population. (If you released server population census, the data will show this.)
Why is an imbalanced server a problem? When a PvP or PvE server is this unbalanced, you have catastrophic problems. The AH markets on a PvE server will skew. The lower side will not have access to many resources. On a PvP server, the higher faction will camp things like Blackrock Mountain. I kid you not when it could take over an hour to get from the flight point to a BRM instance. In some cases 2 hours of corpse running to clear an instance that takes less than 2 hours. You might spend OVER 50% of your time getting to the instance. Battlegrounds coming out sooner will not solve this problem. If queue times remain high, the higher faction will continue to camp the world at an unprecedented rate. Is a PvP server riskier? Sure is! But what was a semi problem in Vanilla is now a factory camping farm in Classic. It is completely unacceptable to ruin a factions presence with FST.
Why is this a problem now and not in Vanilla? There is 2 reasons why a lopsided PvP server is a serious concern. Sheer numbers can change the fact of camping an entire zone or town. This was not a serious concern in Vanilla because rarely did a faction have the numbers to camp EVERY zone and town/fp on a continent. Blizzard implemented 2 features to help this, higher level guards who also had guns and dishonorable kills on NPC. That was great, for that size population. Now with our increased population we need that boost again. Make guards level 65, make them WRECK and have high hp/armor. They are a joke. A town should be a safe place to get quests and items. Dying in Everloook/Gadget repeatedly all day and night is unacceptable. BOOST THE GUARDS.
How to solve this problem. Immediately STOP all FST from the lower faction population. Restore the server by allowing others to FST back to the server. For example, Server Tyrande has 15k horde and 5k alliance. Server Rexxar has 15k alliance and 5k horde. Allow FST for horde from Tyrande to Rexxar. Allow Rexxar FST from alliance to Tyrande. Work to make the server closer to 50/50. If you don’t, many people will quit/unsubscribe. This ripple effect has a way of influencing many others.
You need hasty counter measures put in place from allowing these servers to slip into an awful state of no return. If you don’t, you will never have to worry about queue times because of the sheer amount of people quitting.