It's more that the Feral Flare was literally created to change the fact that Wriggle's was trash that nobody bought... and a few weeks later Wriggle's 2.0 is nerfed back into trash tier because people don't like coping with change. This is the same sort of thing I've complained about before; nobody is denying that Feral Flare needed a nerf, but Riot pulled out the sledgehammer when they should have been reaching for the ball-peen. Wriggle's was always a good item for farming in the jungle, but AFK farming in the jungle is boring and hurts the team, so nobody ever bought it. FF was a good idea: you take the farm item and give it some usefulness in dueling/ganking (but still less than the other options) and give it stats that scale into lategame if you've been farming consistently, so that you're balancing the fact that other options are better for the early-mid game. And then, worried about the exact same things that made Wriggle's trash before becoming an issue again... Riot decided to turn FF into pre-FF Wriggles with a slight boost to AA damage.
Put another way: The reduction in clearspeed combined with the ability to build pre-transform stacks on assists and kills was a good idea. It could have been followed up with a minor nerf, maybe reducing the scaling on the magic damage on-hit to 25% against champions and reducing the gain to 2/stack, or something like that. Instead they removed just about everything that had made the Wriggle's line of items viable for the first time in a long while, particularly the stacking health gain. 10 health/hit is nothing; even if you've got maxed attack speed that's only 25 health/second, which is peanuts compared to a lifesteal item with even 1-2 other items, most notably because health gain on-hit, unlike lifesteal and spell vamp, isn't affected by things like the passive on Spirit Visage.