OH GOOD CALL ON THE BOOTS. I felt like I was missing something. I wondered why I had a space and filled it with the Whisper.

almost good, but wrong, heres why:

Start with E, at 1st level is does a little damage and some nice CC in a big area.

Max the W to avoid having a dire early game lane presence.

Max Q second, but get a point in it at level 4.

9/0/21 is far more effective that 21 in the attack masterys - damage is not an issue for kog maw. and the move speed, flash and summoner spell masterys give you much better and more consistent escape tools. the damage masterys really arent that efficient, your the only ones really worth taking in that tree are exhaust and spell pen. cooldowns, flash, move speed and increased buff duration are all very relevant, as kog is gonna be wearing the red & blue buff a lot and he's not the quickest of champs.

Start with bloodrazor (if you finish this first, you should be finishing it around the same time that their atmogs/fratmogs champ has finished their first health item, which when combined with W, essentially negates their warmogs and allows you to keep them from getting that atmas for as long as possible), then wits end, then malady. Most wont be building magic resist until at least the time when you're getting the malady, so it doesnt really become relevant until mid-game.

black cleaver before bloodthirster? your looking at about 2.2 attacks per second by this point, so the attack speed is moot, and on a team with good team comp and kog, your going to be dealing mostly magic damage prior to your bloodthirster (as by this point your jungler and solo top will most likely not have an atmas), so the armor reduction is moot, especially with the armor pen runes. bloodthirster at this point is a lot more effective, although it may be worth considering a hextech gunblade (not traditional in this build but very, very effective - it should bring your AP up to increase the % damage from W, and the spell vamp/life steal is very very tasty).

and last whisper? assuming you've built black cleaver, theres not really a great deal of point in building yet more Armor Pen (especially with the runes), moreover, the 40AD isnt really anything to write home about. And on top of this, there is not room for a glass cannon in the current meta, so this slot should really be saved for something defensive, think banshees (my fave defensive item on ranged carrys - in this build what you gonna do if morgana snares you? what you gonna do if sion stuns you? what you gonna do if you get exhausted? (your gonna die thats what).) the health and mana and MRes are nice as well.

but if you really wanna go the glass cannon route, you'd be better avoiding the cleaver and the last whisper, and selling your boots for 2 phantom dancers, this route means you can even sell the wit's end aswell, making room in your build for another bloodthirster, or the tasty tasty hextech gunblade, hell with the 2 phantoms an infinity edge isnt out of the question.

The runes arent dreadful, but I would recommend: flat AD quints (greater early game harrass), flat Magic Pen Marks (this build deals far more magic damage than physical, and your going to be seeing far more mercury treads than ninja tabi early game), flat armor seals (what good is 12.6% more attacks if the caitlyn has AD runes and repeatedly shoots you in the face?) and MRes per level glyphs (these are just the ****ing boss glyphs).

also, theres no boots in this build? i think (hope :P) thats a mistake.

Very nearly a good build.