I have heard bow DK work in PvP, though I have yet to try it out myself. Green dragon blood is a must and I think eruption is a good idea as a back up plan / safety valve if you get rushed. I would put those together on one bar and maybe even pick up obsidian shield. Molten armaments will probably do a lot for your DPS so I would put that on a bar as well so you can buff before you enter combat. Engulfing flames is a mana hog, the fire dmg bonus is nice but you would probably get that from MA and be able to keep MP for other skills i.e. shield / eruption. I would consider the dragon leap ability for your ultimate. It does nice damage and since it knocks everyone back you can erupt and get distance so you can work with your bow and I believe it also works as an escape so again if you get rushed it might help get some distance for you so you can work the bow and/or run away if needed.

Interesting build I would be curious to know how it goes for you. I have been wanting to play around with bows on my DK as well. Hopefully it works out!

Just thought that I should add that now the PTS is open to everyone. I intend to download it and test out my builds before I commit in game. I would advise you do the same since the cost to respec is astronomical IMHO. Approx. 17k gold at VR1, which was 2/3 of my savings as a player that has focused on leveling and questing.