Campaigns are in serious need of balancing. I hope ZOS realizes if they ever hope to achieve balance, they will need to regulate where players go. Bloodthorn was relatively fine with low numbers from all three sides the first day. The second day, an EP super guild/alliance flooded their faction and has completely dominated the campaign since purely on numbers.
They have consistently been camping EP and DC at their respective spawns and many in both of those underpopulated alliances have campaign-hopped. AvA, with perhaps the exception of Auriel's Bow and Wabbajack, has been an absolute disaster for most of the campaigns.
Alliances are lopsided. Players are switching to whichever campaign they can dominate and easily crown an emperor. AvA was never this terrible in beta and I seriously hope ZOS is paying attention. If these population issues are not addressed sooner rather than later, they will see their PvP community will start to leave the game in droves.
I say this as a long-time PvP veteran and having experienced poorly-regulated PvP leading to dying communities. This is absolutely an issue that needs to be resolved immediately. By far this is my biggest concern with the game as it currently stands.