"Unlike basic attacks, no two abilities are the same, which makes the stat wildly variable in value"

"Let’s start by comparing it to lifesteal. Thematically, lifesteal gives the feeling that you’re fighting back against death, creating tense 1 on 1 duels with uncertain outcomes. Mechanically, lifesteal says ‘I may have a small health bar but you’ve got to focus me down or I’ll regenerate to full.’ Spell vamp, while sounding similar, doesn’t quite hit the same bar. Unlike basic attacks, no two abilities are the same, which makes the stat wildly variable in value.

This means that it’s functionally impossible to make spell vamp work the way you’d expect, and it instead operates on myriad edge-cases to avoid feeling abusive and unintuitive. Cut to today’s world where it’s only used on Vladimir (whose balance is kept lock-step with the stat), it’s easy to see why it had to go."