It's probably a sensitive topic for me to comment on, since I'm a Bladedancer myself and people love to point fingers, but I get OP's main critic:
if you think about MMOs and RPG dynamics in general, it's indeed quite unthinkable that a caster/support/priest-like class wearing leather/light armor would have more physical defense than a half-tank (let's not forget that BDs shares their first class with SKs, which put both classes together on the progression tree) wearing plate/heavy armor.
I'm not saying OP's proposal of solution is the best, as many people have already pointed in this thread, but this should be definitely a point worth of the staff's attention if class balancing was ever an issue they are willing to address.
