Oversight or intentional?
Greatsword attack for Guardians, Binding Blade attack puts an effect on the target that does damage over 10 seconds. This damage is only modified by increasing condition damage and it ignores power.
Logic infers that since this is effected by an increase to condition damage, then condition duration should have an effect on it as well. Especially since condition duration is a trait line that has a lot of greatsword enhancing traits in it.
Increasing condition duration has no effect on binding blades duration. I think it should based on other mechanics.