"Smart" Spellvamp Would Fix the Stat

Right now spellvamp almost universally sucks because the vast majority of magic damage abilities are tagged as something other than single-target: aoe, pet damage, or oh-hit magic damage. Thus, the vamp effect is immediately reduced to 1/3. On that's a whopping 5% of your damage, and spending 3 quints and 5 mastery points gives you a total of 2.6%.

SOLUTION: Just have all spells apply spellvamp only to the first target that is damaged. Problem solved.

In addition, allow kit-based on-hit magic damage to apply spellvamp at 1/3 effect. It sucks when a big chunk of a champ's damage is walled off from applying spell effects altogether, like Teemo's E and passives on Diana, Ekko, Elise, Brand, etc.

RATIONALE

First off, single-target spells are the exception, not the rule. When you review the tags it's clear that the spells most rewarded by spellvamp are mostly high-damage unavoidable point-and clicks (Cass E, LB's QR, Annie's Q, etc). In other words, the overwhelming majority of aoe spells are skillshots, and it makes little sense to penalize that.

Second, in the context of a 1 v 1, every spell is effectively single-target. Malz' Q takes up space, but in a 1 v 1 it will only be hitting 1 target. It doesn't make sense for him to be penalized for targets that don't exist and weren't damaged.

Other spells suffer the same problem. Lux's and Veigar's Q only apply 1/3 even if they hit only one target, but they're double-penalized in that these kinds of "aoe" spells can't actually hit 3 targets to break even or 4+ targets for a net gain. It's the worst of both worlds.

Then there are spells like Morgana's R and Katarina's Q that are legitimate single-target abilities if conditions aren't met. For example, Morg hits R on a single enemy and it applies at 1/3, but if two other enemies walk into the zone the ulti doesn't attach to them. Ditto Kat's Q if it doesn't bounce. There is no true area of effect for enemies to wander into, and there is no space or zone occupied by the ability to justify 1/3 vamp effect.

Pros and cons? Discuss.