Hey Elementz, I just wanted to drop in to say that I'm a big fan of your tier list. It's great that people of such high elo and high community standing like yourself are providing such a service for the LoL community, and I thank you for that.
Moving on to the list itself, it's great, and I like the work you've done with it and all, it's just sad for me to realize that every character I've ever had serious interest in is in tier 3 or lower. In particular, the two new champions that I've considered maining in the past two months, Malzahar and Kog'Maw, have fallen to the bottom of the list. In the case of Malzahar, this was ok because it made me realize how bad a champion he is in the current state of the game and move on, but in the case of Kog it only makes me want to ask why you think he's fallen so low. I know you already briefly touched up on him, but I'd like to bring up a few points about why I think Kog is a viable champion. Certainly not top tier, but definitely viable in this state of the game. (For clarification, after failing with the Phreak build, I've strictly built Kog as AP, and I feel that's the best build for him)
One thing Kog has above other casters when built AP is he scales a lot better as the game goes on. I think of Annie in particular when I say this. She is at her scariest mid game, where she has her full stunbear combo and decimates squishies and non-squishies alike. This is the stage of the game where Annie beats the snot out of everyone, and hopefully a fed Annie can end the game before the 30-minute mark. But I know that once the game gets to 40-45 minutes, Annie's damage potential against a well-built team drops considerably. I feel like I'm only good for my stun at this point in the game, and while they're stunned my carries/other dps mops up their team, which is an invaluable role, but the point is her damage potential is severely lacking after a certain point in the game, unless she is superfed. Many mages are like this.
Kog, when built AP at least, gets the best of both the mage and dps worlds: he gets very strong damage potential when he hits 6 (and at a considerable range), and his damage potential stays strong throughout the late game thanks to BAB. This is the reason I buy Nashor's with AP Kog, because the attack speed increases the dps potential of BAB by a boatload, all the while helping your Living Artillery and Void Ooze pack a solid punch.
I think one of the other things that keeps Kog from top-tier levels is his lack of an escape mechanism. This is a valid concern, seeing as Kog is as squishy as he is, but the reason he doesn't have an escape is because of his ridiculous range, therefore he shouldn't be in the front of teamfights in the first place. However, I find people tend to underestimate Kog's escapability. Void Ooze is one of the top three slows in the game in terms of sheer slowing %'s (I believe Singed's ooze and maybe Nasus' single-target slow are better), and when combined with a Rylai's, it's very possible to use Kog's slow to avoid nasty encounters with the entire enemy team. I've used Void Ooze to save my allies' skin multiple times when they're trying to elude enemies through the jungle, and it works wonders for this purpose.
While I do agree that he does have some glaring weaknesses (no escape mechanism, fairly item-dependant, Q is pretty useless in AP build/E and R are useless in a DPS build, many mana issues), I do find that Kog is far from "hard to place on a team." I use him regularly with my friends when we premade, and I've had some great success with him. Granted we're not high elo, and we haven't used that same setup since the stats restart, but I've carried our team with Kog'Maw more than once in the past, and I think he's a good choice as an AP carry.
Also, sorry for the wall of text. I just kind of typed whatever I was thinking, and let the thoughts flow. Sorry if it's too much.
tl;dr: Kog'Maw has mad deeps, brah. I think he's better than bottom tier.