Building Grievous Wounds (a status effect that reduces healing; useful for countering lifesteal and sustain except shields) on:

Ability Power-Based Champs (Mages): -Generally a good idea since the item that grants it is pretty decent (Morellonomicon)

Attack Damage-Based Champs (ADCs): -Not recommended; the item that grants it (Executioner’s Calling) isn’t worth the gold (15 AD for 800 gold; literally 5 more AD than a Long Sword that costs 350). It doesn’t help that ADCs are extremely item-dependant and need every singe gold coin they earn.

Tanks: -Not recommended; there’s no useful item for tanks that also grants Grievous Wounds. Plus most tanky characters have a form of CC to stop characters from sustaining (in most cases).