Some CCs are better suited for PvP than leveling and vice-versa. In mixed mode it would be nice to be able to use a different CC when in a battleground.
If you're doing mixed AV, which I hope you do cause it's the best way to level. It doesn't really matter what CC you have, seriously. On the other hand, you could switch to another AV profile so it defends the towers and help kill the bosses. That's what I did and it works great for me, but winning and losing has only to do with luck, sometimes I win 70% of the times, other times I lose 70%.