Kog'Maw; A Quick Change
This is really coming down to placing some kind of power back into Q that players will find worth putting points into it and maxing it; also other things I will do to tone back his current power and try to make feel like he needs more levels for his hyper marksman status will turn on, same goes for hyper mage status, but I do not think AP Kog'Maw is a problem right now (AP Kog might be a little weak right now actually).
This is still a discussion post, so share your thoughts and ideas on the topic at hand to see how you would improve on Kog'Maw to place him in a good balance spot.
Caustic Spittle (Q): Passive: Kog'Maw's basic attacks deal 10/20/30/40/50(+25%AP) bonus magic damage on-hit.
Active: [Damage reduced to 80/105/130/155/180(+50%AP) from 80/130/180/230/280(+50%AP)]
Bio-Arcane Barrage (W): Passive: [Attack speed adjusted to +1/1.5/2/2.5/3% per level from 15/20/25/30/35% flat]