I mostly play pantheon so gonna talk from that perspective. Generally have SoJ and TBC for a little tankiness so thats +650 health.
Darius with TBC and no other damage items: Q, W, auto ult and im dead even if im fed. If its a teamfight/skirmish and I have taken some damage already QW ult kills me straight up.
Cho gath just killed me missing his knockup, silence, auto, ult. Only dmg item he had was liandries. His ult killed me from about 55% hp.
Then theres garen. TBC no other dmg item, spin around you a little, q and ult pretty much anyone that isnt a tank or building a number of tank items is dead.
Its stupid how easy it is to kill with these champs. Not to mention darius' ult resets. And even without SV or deaths dance in teamfights he can build so tanky and heal half his health from a good Q. which has a short cooldown.
these champs and this mechanic needs to be looked at seriously.