Coming back, have no idea what to do.

So, I've not played in over a year. In wotlk/cata I played a DK, on Draenor EU (horde). I'm wanting to come back, but I have no idea how each class spars up to another in MoP.

I've considered a monk, and a warrior, but I'm not too sure. But that isn't the main point of this post.

If I were to pick a pvp server, EU, which should I go for if I want to roll horde? At the start of MoP I know a lot of realms had crazy wait times, but I'm not sure if it's still like this. A lot of these.. err.. "realm faction population & balance" lists don't really seem accurate to me.

So, with your personal experience/previous choices in mind, which realm should I roll on if I want to do Horde PVP (EU)? Draenor was a PVE server, and it isn't that active. I like active servers.