User blog comment:Degritone/Tonan, the Essence Thief/@comment-7709681-20141117025001/@comment-7709681-20141117044807

Well, is not correct, as it stands says that he heals for an amount equalt to his mana, and what you want is to get spell vamp per max. mana.

If I calculated correctly with your example, then you could worded like "Gains 3% Spell Vamp for each 100 max. mana", much like other convertion passives; however, I must tell you right now that's a ridiculously enormous bonus (He's innately getting 8.61% (1.89% per level) Spell Vamp, that's 42.63% Spell Vamp at level 18. He'll need to build just 1912 bonus mana to get 100% Spell Vamp, or get an item with 20% Spell Vamp plus building 1246 bonus mana), is far too overpowered.

And doesn't matter if Mana Burn is what the kit centers on, it was eliminated because of its toxicity, it didn't allowed the affected opponents to play because they didn't had the cost to do so, so were born the alternative resource as a soft form to swiftly eliminate such effect from LoL (And that's why, in both examples I gave, the Mana Burn got replaced with just magic damage on-hit).

Additionally, even if it was something that could happen again, in both examples was a single source of such effect (A single ability or autoattacks), here we speak about having the entire kit eliminating the targets' resources, aswell as getting horribly countered by manaless champions.