Lay Waste and Frostbite Crit

Lay Waste (Karthus Q) and Frostbite (Anivia E), when dealing their double damage, interact as though they are critical strikes and hence have their damage reduced by Randuin's Omen. They are not, however increased by Infinity Edge or healed off of by Warlords Bloodlust.

How is it that they are allowed to have the downside of critical strikes without the upsides.

The I.E. interaction doesn't bother me as much, since I don't often build it on either champ, but I was really excited to use this keystone mastery and have some real sustain on Karthus.

I think that either they should have all the interactions or none (since Randuin's is an armour item that also gives random protection from a couple of AP champs by accident.)