What champs build spell vamp?

Obviously AP champs, probably melee, would build spell vamp, but it doesn't seem to scale well. I mean, for Eve, wouldn't you more likely live through an assassination by adding more AP for burst than spell vamp for dueling?

All I can think Akali, Eve, and Diana. Maybe Vlad, but he seems to get by just fine only using Will of the Ancients. Morgana even has spell vamp in her passive, but I would think spell vamp for her would be a consideration after AP, CDR, and probably every other stat. Other champions have heals or health gaining abilities within their kits, like Tryn and Ali, but that Visage alone would be a better item than building AP for them.

Even Will of the Ancients specifically says you gain health based on a percentage of damage dealt, which seems like it's the same thing as saying spell vamp, but why change the specific wording?

Spell vamp seems like a cool stat, but is it out dated with so many champs bringing heals through their kits?