I voted Vengeance, but didn't leave any explanation. Hiro pretty much sums it up. You can hit out pretty quickly without needing, or searchign for, leech. It has some nice AoE and still pretty fast.
Just yesterday i compared streams with "the best twink of my realm" and i found out that he's not so special compared with my times. 8-10 min dungeon is still pretty fast for the people who want to lvl up.
5 hour full boost, compared to the "less than 24 hrs" bots in trade channel is good competition.
I run 20+ dungeons per day as Vengeance, 10 min average run every time.
Havoc has no defense, DhT and HoV will for sure be tricky if you want to compete with full pulls. I'm not convinced the artifact weapon will be too special at 101, also keeping in mind you don't have the extra silence on demand as vengeance has.
Be racial, Sigil of silence are really essential for DHT and HoV.