Should there be something done about instant Execution ults?

I'm talking about point and click kills like Garen, Cho Gath and Darius. In my own ideas I think they should be nerfed, not in numbers. For example: If Garen Ults on a Ap champ on 1/4 hp and the ult is active already. Then the ap champ uses Zhonyas, it should put the ult into cooldown. It's just not fun to sit there and wait to be ult'd down and just not able to do anything but wait for the stasis to kill you. If you cannot cancel these ult out, why give the ult a .5 second reflex to the ult? Might as well just execute on point if it's the thing. Darius' ult gives plenty of time before he dunks, Garen does so too. Cho is almost instantaneous but you still can Zhonyas it before it strikes.