If Kog still needs buffs after the %HP damage increase
Why not give him back his full W range again?
Waaaaaaaaay back in Season 1/2 Kog had 750 attack range when his W was active. He was pretty decent in the midst of the MetaGolem era, so Riot gave him a bevy of nerfs, including knocking his W range down from 750 to 710. Rather than upping Kog's damage (which is, quite frankly, a dangerous thing to do) he could get his real distinctive back. Namely, the longest ranged Marksmen apart from Twitch using his Ult.
buffs have brought AD Kog'Maw back up to 50% win-rate. Any further buffs would push him into being too strong.