I would disagree with you on this issue. I have been playing a lot of Crucible and Iron Banner of late and those players who go Bladedancer that I do encounter have always tended to score quite highly on the post match tables with K/D ratios above 1.5. One on one their super is deadly and I've seen them take out Sunbreakers mid-super and against more than one opponent I've seen them score multi-kill around control points/relics/heavy weapon ammo. Bladedancers are the closest thing to an assassin the game has, you use your increased to mobility get in, cause as much damage as possible to your target(s) and then get the hell out of there before any survivors can react. Most people forget these tenets when playing Bladedancer and wade right in wondering why they get creamed when they stick around too long.