I had a Horde alt there and I do fine on it. Lots of Horde and the community is good but tbh it's like any other, there's just more people. Just because Kazzak scores high on the raid progression doesn't mean that all or most guilds fall into this boat, there's often a handful of guilds who raise the bar above average.
But to just throw it out there like I do with every other thread like this:
Kazzak is great for raiding and has a very large Horde community. It's PvP community is nothing special but is ofcourse larger because of the size of the realm, just bear in mind that you will not find world pvp on this realm.
I also don't know your preferences so I will throw another realm out there for you - Draenor. If you are considering playing on a Normal realm without the risk of being ganked then go Draenor. There is less PvP and obviously next to no world pvp because of it's type. But I want to throw it out there because there are a lot of people out there who forget about Normal servers and just look at the #1 progression server which is often a PvP one. You appear to want some PvP but i just to throw it out there to broaden your scope a little.