Change Skarner's Q or Passive to deal % Max HP Damage

http://ddragon.leagueoflegends.com/cdn/img/champion/splash/Skarner_3.jpg

So like all of the tanks have or are getting % HP damage. Skarner is considered a tank or a bruiser/fighter depending on how you build him, but I think his tank build is considerably weaker than other tanks. Building damage on current Skarner is tricky since he has mixed AD and Ap ratios and they're all quite low ratios. You used to be able to stack AP and be a damage dealing healing AP bruiser type thing, but that doesn't work at all anymore.

I propose that he gets the same treatment as other tanks and gets % of Max/current health damage somewhere in his kit. He's one of the few "tanks" that doesn't have such an ability. Sej, Zac, Maokai, Mundo, etc ALL have spells like that. Let him join the club maybe? He is not that popular and I think this would help him see more play. He tickles people late game I find since he doesn't have high damage scaling. % Hp dmg just makes sense.

I know the tank meta is sort of hated at the moment, but Cinderhulk is getting nerfed so I'm sure it won't push him over the edge.