Only speaking from the Xbox said because I'm not PC or PS.
Back in the day locking the campaign needed to be locked because there was a lot of players in the game and some would Q for one alliance then switch alliances real quick to lock the Q up on other alliances. Now of days once you pick the alliance you are locked into that alliance the whole month. The problem is guilds/friends are rotating alliance every month setting an imbalance to and alliance in PVP almost every month as of late. Then you have to wait a whole month to see if will balance out for the next month. DLC makes this far more noticeable but the imbalance has been around for sometime now.
I'm still for the Locking of alliance but feel that the Campaigns needs to have a floating lock on how many people, can be on one alliance, at one time, during the game. With one alliance never exceeding more then 25-50 players (after 1 bar) more then the other side. This might make other campaigns more active but would help keep the main campaign viable and more competitive.
Going into the main Campaign and seeing one alliance has everything on the map and has a full 3 bar alliance to both 1 bar of the other alliance makes people not even want to be in Cyrodiil. There has to be a way to balance Campaigns better so month after month there's more far game-play. As of late the unbalanced alliance in the main campaign has been more noticeable.