Sion's passive punishes him for gaining levels

Sion is intended to be a hyper-scaling tank with serious threat from his passive in teamfights. Yet his passive has to be the worst scaling ability in LoL for one reason: the health drain scales harshly with level.

Each tick of drain is proportionate to 1+Sion's level. This means that the drain is 9.5x more intense at level 18 than at level 1. Sion starts the game at around 550 health, so to keep the drain proportionate, he'd need to have well over 5000 health end game. That's an absurd amount of health even with a pure tank build and healthy w farm, unless you build 0 resistances. So you'll bleed out faster late game than early game.

Then to make matters worse you have 0 scaling of the dmg or attack speed into late game, so anyone who buys armor will take minimal dmg even if you somehow get to them and stick. The net result is that Sion's passive is amazing early game and can easily net multiple kills in a lvl 1 or 2 fight, or steal the enemy's red/blue buff camp. But late game, when Sion is supposed to be at his strongest, the passive dies in a matter of seconds even with no enemy action whatsoever.

Therefore I propose Riot change the passive scaling to a % of base health (not sure exactly how much, but enough so that it's a nerf early game and buff late game), so that the passive has consistent strength across levels. This brings the drain scaling to about 3.5x as much level 18 as lvl 1. This way cheesy early game strats like the buff steal are less effective, but the passive feels less frustrating late game and forces the enemy to pay some attention to your lumbering corpse.