Rek'Sai ult bug

While Rek'Sai is vanished underground during her ultimate (for 1.5 seconds), it still counts as being in vision for purposes of resetting Duskblade, even though you are completely invisible for more than 1 second. Honestly, I'd trade Rek'Sai's undodgeable ult for a fix for this. It makes no sense and is annoying.