Ok lets remember here, what was the purpose of Grevious wounds? it's aim was to counter healers, life steal and spellvamp and thats good right? Champions like Vladamir, Zac, and of course those double lifesteal ADCs can be hurt but not shut down and countered.
Then pray tell then Riot, why you think its a smart idea to add more means of sustain (WoTA change, BOTRK, Elixirs, Spirit visage change) but you remove its main means of countering it.
Fizz W? Gone
MF W? Gone
What's the point of Soraks ult removing Grevious wounds anymore if your slowly phasing it out? lets just remember here there are only FOUR things that apply it now
So you have a choice of a champions weakest spell in their entire kit, an ult which only lasts until it gets one kill then spam those resets, an item which only applies it at 40% or lower or a spell with over 3 mins of cooldown. This just means sustain will go hand in hand with tanks and we'll go from a tank meta to a tank+ Heals meta, we're talking Nauts top Tanky junglers Vlad mids and the return of Sona and Nami (Ok I'm all Yay for that last one)
Rather then just flat out remove this "hidden power" why not move it to other things? say Iunno, what if attacking a person with Thornmail applied grievous wounds as well? what if a new item for say brusiers applied grievous wounds when activated?
I mean if your just phasing out the debuff why not just say "hell with it" and remove it from everything minus Ignite since y'know, over 3 mins cooldown? kinda not gonna worry sustain champions.
Wouldn't be suprised if thats in patch 5.15