I noticed the same thing. Same problem occurs with Superior Rune of the Undead [(6): 7% of Toughness is converted to Condition Damage] which is a more general problem inflicting every profession.
It appears that condition damage from percentage properties is only calculated on the basic value of toughness or at least not updated correctly in the hero overview. Maybe I’m going to make some damage tests for further investigation in this case.
Elementalist – Der Rat der Berge [DRDB]