Is this a good random BG class? and in MoPtoo

Hi guys I am looking for a long term main and I have really been enjoying DK. However I am still only level 71 and low level bgs are about meaningless in terms of finding out what a class is like in PvP at max level. I would mostly do PvP on the side in random BGs but that is important to me so would this be a good choice for those? Also what about long term in MoP? That is important to me. Thank you! Any info you can give would be great.

Also in general info on if DK would be a good main in general would be nice too.

I am currently sitting here with my war at 74 and my DK at 71 and not sure what to do. War seems a little too easy to play and I enjoy the complexity and style of Dk but I dunno, as I haven't actually experienced them at max level I may be wrong about that.
It just depends on what you like really. DK's (unless you're blood) are caster/healer killers, and have trouble with other melee. Warrior do well against a mix of everyone with strengths and weaknesses against different classes.

DK's are good in BG's because you can really rip people up, but if you're focused you're dead (unless you're blood).

DK's are a good main in my opinion because soloing is cake with blood spec, although you don't have many transmog options, you can still build a nice set.
So you said unless your blood a lot does that mean that BLood is bad in PvP then?
Blood is crazy in 1v1 scenarios against other melee. You have the killing power, tank cool downs, and best of all, self healing that gives you an absorb shield with Death Strike due to your Mastery stat. Blood is good in BG's and duels against other melee, though you are easily kited. Frost and Unholy aren't that good against other melee, but destroy casters and healers. So it's your choice of what to play.
Ah I see thank you very much.