At its core, Goredrinker is supposed to be a sustain Mythic that lets fighters outlast their enemies with well-timed Thirsting Slashes. While wanting to sustain through a fight isn't unique
to fighters, it's a big part of their class identity: They have the best tools to stay on the offensive at low health (ex. the dream Illaoi ult that lets her turn a 1v5). At the same time, this is a risky niche to fill: Two of our bigger rough patches since the item update have been damage and healing, and Goredrinker offers both.
We've seen this risk play out over the course of the season, with Goredrinker becoming the dominant Mythic pick for fighters due to offering the best sustain without making sufficient tradeoffs on the damage front. As further evidence,assassins have been taking Goredrinker over their own Mythics. Assassins are designed to kill quickly, so they shouldn't be valuing an item that indexes so much into sustain and strength at low health. Between its 1.0 AD ratio and its heal, Goredrinker's active is just too valuable as another button in assassin combos that also lets them shrug off any damage they take while eviscerating their target.
In order to move Goredrinker back into its sustain niche, we're removing its low-health bonus AD (to nerf damage for fighters) and weakening Thirsting Slash's AD scaling (to nerf damage for assassins). At the same time, we don't want Goredrinker to become a bad
pick for fighters, so we're giving it omnivamp to make sure it still lives up to its identity as their sustain Mythic.