Kog'Maw passive needs to be reworked

No matter how you play him ad or ap, kog maw is a carry. Having a passive that might reward you on death for a carry is stupid especially in 2015 where almost every champion has a dash or speed boost to avoid his ult. What I propose is a passive based on his identity as a hyper carry anti-tank with radiation as the theme.

Passive Radiation: Every hit or spell cast on an enemy champion applies a stack of radiation for 5 seconds refreshing every time a new hit is applied. When 4 stacks are reached, one permanent stack of tumour is applied. Tumor: Double stacks every five minutes, enemy gains +1% health regen per stack and 1% size increase per stack (hitbox get bigger) but take 0.5% increased damage per stack; at 100 stacks the buff is consumed and replaced with Cancer. Cancer: Enemy gains 200% health regen. Enemy loses 1% of current max HP per minute and take 50% increased damage.

Wouldn't this make Kog'Maw broken?

Not really. You'd need to hit an enemy four times before they even get one stack of tumour. To actually get to 100 stacks would take a while and since a game is about 35-45 minutes, you'd only have your stacks double 6-8 times if you started hitting the right at the beginning of the match.

What if my carries get Cancer? Your carries are supposed to be in the back line where it's hard to Kog maw to apply his stacks consecutively. His passive was designed to give the enemy back line more of an advantage while enemy front line a disadvantage. If you're back line is eating 4 hits from an immobile hyper carry all time time they deserve to get Cancer. (The buff obviously)

Wait, current MaxHp Reduction? How does that even work? The cancer buff should activate on front row at the 35-40 minutes mark so at that point I'm going to assume tanks have about 3k hp. Now, every minute their current max hp is reduced by 1% so it'll look something like this.

40m: 3k hp 41m: 2970 hp 42m: 2940.3 hp 43m: 2911 hp 44m: 2882 hp . . . 50m: 2713 hp which at that point most games already have ended. If you let it drag out to 60m your tanks will probably be at 2450hp. Remember, hyper carries are meant to be OP late game.

How do you counter him? He's immobile. Either hard engage him or out poke him. He has no escape and relies on the team to peel for him to actually even do any damage. If he get 2-3 radiation stacks on you, leave before he gets the 4th one turning it into Tumour. If the passive turns out to be more op than expected Riot can always nerf it.