Grievous wounds

Why bother having healing dependent champs like aatrox or soroka when it's so easy to apply 40% reduction of healing on any champ you want to kill? I could understand if there was some way of cleansing the debuff or it having some delay between procs on or , I understand this is supposed to allow counterplay for healing, but since almost any champ can build them without making their build much worse all heals have to be stupidly strong to be substantial, and it makes champs with the grievous wounds effect less impactful using it since its so easy to get.