Vlad's E NEEDS to feel satisfying when you land it, regardless of target.
It should ignore a certain % of bonus MR (or even all of it) considering he's dealing 10% max HP true damage to himself every time he uses it.
Before anyone says it, yeah he's probably eat nerfs somewhere for this, but the kit, as it stands, will never be rewarding. It expects one specific scenario from your enemy: Glass cannon melees who ignore all of the warning flags. If your enemy doesn't match that description, you lose more often than not. Simple as that.
Vlad never feels decent if there's even one tanky champion on the enemy team, considering you're giving up a good amount of CC by picking him over another top laner. Even if you land E, its a win for anyone that isn't glass cannon, cause you do more to yourself than you do to them.
TL;DR, Vlad deals significant true damage to himself. Make it actually rewarding to land when it hits someone with any form of MR by ignoring a % of their bonus magic resist.