What changes happen in PVP zones?

Callista is a mega powered PVE killing machine, EMP, GDF, fireball -> dead mob

Hold, tab, hold, tab, hold, all enemies held now go get em team.

However when she steps into a PVP zone something magical happens. Firstly she trips over her shoe laces ... well ok not quite, I know they changed some powers for PVP zones but I don't know what??

I got an action string more like, Hold, miss, hold, miss, immob, miss, hold ... ah got him, oh no he's free again ... eh that hold only lasted 1 second, AS -> dead

Controllers are feared in PVP but is this just image, or am I doing something wrong. I almost universally have my holds and immobs slotted for 2acc, 2dmg, 2dur (go ED). I still dislike PVP and won't be going there but it would be nice to know why things go wrong for me so quickly. I'd also like to go and get the badges sometime at least (Callista is my badge character).

I also can't remember what powers change, or how, in PvP. However, my suggestions would be:

Slot 3 acc/2 recharge/1 damage for PvP. Accuracy is needed more (most players have heightened defence), and given that most sensible players will have a stock of Break Frees, it's more important to be able to hit them frequently with mezzes than have the mezzes last longer.

Keep moving. Wherever possible, maintain SJ/SS (or, even better, Fly or Hover) and get out of range as soon as your attack fires off. You can go back if you hit them, but it gives you a slight chance of getting away if you miss

Immobilize comes into its own when fighting tanks and scrappers. Because they have fewer ranged attacks, you can get away with dancing around them throwing attack chains while they try to get out of the immobilize.

Just a couple of thought to hopefully make your experience in PvP zones better...

The main difference is that in PvP zones players have a 25% bonus to base defence. So people usually slot normal attacks with 2 accuracies and often run Tactics alongside to make sure they hit. Controller AoE holds which have an accuracy penalty would definitely need 3 accuracies and/or Tactics to hit reliably.