TFT, Dragon's Claw, and Karthus

A serious bug: In TFT, if Karthus uses ult and one of the target has Dragon's Claw, there is a chance that ALL of the targets take the 83% reduced damage.

I just had a unlucky TFT game in which one of the player put one Darius with Dragon's Claw in front line and then all his other champions enjoy immunity to my Karthus's ability...