Seriously though, why do mages get 8 seconds of Grievous Wounds on their primary item?

That's a stat ADC's have to seriously hinder themselves to build and itemize with, so why is it so free for mids?

It would be tough to argue Morello's being the best mage item in the game even if it didn't provide the added benefit of literally 1 spell grazing Mundo, soaking up 8 out of 12 seconds of his ult. I know it's below 40% that it activates, but Mundo's entire kit revolves around his health being low. I personally like Morello's being a stronger item myself, but why does it provide literally everything outside of survivability? (And depending on your kit, it provides that as well)