@Meddler: I don't think you guys will be able to balance Kog purely around damage

Simply put, trying to amp up his damage to the point that he's attractive as a pick ends up making his damage absolutely crazy. We've all seen what that looks like over the past season. It wasn't pretty. So instead of shoveling buffs onto his %HP W damage or his base attack speed, why not try something a little different?

Why not make Kog THE source for resistance shredding bar-none? So instead of amping Kog's damage to 'insane' we keep it at 'really great' while focusing on his ability to make the damage his allies deal ALSO really great?

Getting this to work neatly would require some changes to Kog's Q and Passive.

Passive - Dissolve: Kog-Maw's basic attacks apply stacks of Dissolution to enemy units. Dissolution stacks reduce the magic resist and armor of the target by (flat value) for four seconds.

Q - Caustic Spittle: Kog'Maw launches an acidic projectile that deals magic damage and applies the Corroded debuff to the first enemy unit hit for four seconds. While afflicted with Corroded, Kog'Maw's Dissolution stacks reduce (percentile value) OR (flat value) resistance, whichever is greater.

It would fit with Kog's acid theme AND it would give Kog a gameplay hook unique to him. His damage would improve a bit, but his ability to improve the damage of his TEAM would improve drastically.