User blog comment:Willbachbakal/(Champion Rework) Vladimir, the Crimson Reaper/@comment-24501229-20150103074852/@comment-1330314-20150106162617

Having a % current health cost means Vlad's abilities always have a meaningful cost, regardless of how tanky he builds. The health scaling on his passive means you'll only lose health if you're at max health with little to no bonus health. With just a bit of extra health, you'll practically always be able to heal more than you'll sacrifice. I'm not specifically trying to discourage a full AP build, I'm just saying it's always going to be inherently riskier and less sustain-focused than an AP/health or full health build.

I'd also argue that a skillshot will always be harder to land than a PBAoE. Whereas right now you just need to press a button once in range, here you'd have to aim at the right target in order to catch as many people in the AoE as possible. The 175-radius AoE is also always going to be smaller than Tides of Blood's 610 range.

While you can restack the passive immediately after using it, you still have a limited amount of uses per target, since it caps at a portion of their maximum health. Even if you were to use it optimally and get the maximum possible amount of damage and sustain, you'd still only be able to use it 2-3 times on a target, so health will always provide more sustain.