I'm really late to the party, but I'd like to share my thoughts on some of the potential suspects if that's ok:
Manaphy - Needs to be tested.
I know that there's a power creep and all this gen, but 100 across the board still seems pretty good, and when coupled with instant 100% heal, Tail Glow, inability to be stopped by status, and the great offensive type that is water, I think Manaphy at the very least needs to be tested, if not banned.
Skymin - Needs to be tested.
Great speed, Great special attack, good coverage, and the insanity that is Seed Flare when coupled with Serene Grace, this thing should probably be banned.
Attack Form Deoxys/Normal Form Deoxys - Unsure
Frailty + Power Creep seems to balance these guys out a bit, but does it really? I mean, yeah, there are things that can OHKO 'em or maybe even wall 'em, but 150/150/150 and 180/180/150 is still pretty insane offensive stats. I can understand if they stick 'round for another round, but I think they'll eventually need to be banned. The fact that they have Extreme Speed means that they ain't as weak to priority as some other frail sweepers are, unless said priority user is a ghost.
Defense Form Deoxys/Speed Form Deoxys - Fine for now
I don't really think these guys are that bad right now. Though Speed Form Deoxys in theory is still a great lead, leading in general ain't what it used to be and though it's bulkier then the other offensive forms, is incredibly fast on it's own, and has above average offensive stats, it's still fairly frail and probably has difficulty doing much of anything outside of support or being banded/specs. Defense Form is just a giant wall and seems like it would be the least broken of the Deoxys Forms assuming any of them are truly broken. I think these guys should stick 'round a little longer and see what happens.
Dory... Mole thing - Unsure
Weak to many forms of Priority and can have difficulty getting 'round certain walls may help balance the mole a bit, but being bulky enough to take most forms of priority like a champ and having ways around some of it's counters coupled with it's ability to be stupid fast in the sand and being able to hit decently hard even without setup (and even harder with setup )... I dunno. I'd say leave it for now and see what happens.
Darkrai - Needs to be tested
He hits pretty hard and fast, has really good coverage in two moves (given, one of those moves just so happens to be one of the most trolly moves in the game <_< ), and an accurate sleep move (when compared with most others ) makes for a pain of a 'mon. I'm not sure if it needs to be banned, but it should at least be tested.
Drizzletoad - Fine
This is probably just Yugioh logic coming in, but in my eyes, Rain is only as broken as the 'mons that abuses it. Now, thanks to lurking alot awhile back, Rain seems to me like it'll always be borderline on being broken since it does give some incredible support to it's abusers, but that's my outlook on it. Now, if everything or most of everything that abuses rain is broken, then... Have fun with that, guys XD
Inconsistent - Needs to be tested
I could see Inconsistent being banworthy, but not because it lacks counters, is difficult to deal with, or because it breaks Evasion Clause. I can see it being banworthy because it's simply outright bad for the game, or at least it seems to be bad for the game. It's like a double barreled game of Russian Roulette where one of the barrels just happens to be pointed at the user, and who likes that? The only sure fire counter to it seems to be luck itself... And maybe Perish Song... And I suppose Unaware could be good... Erm, point is, it introduces a lot of luck into a game that's already luck based and while removing all luck would be unreasonable (Though, I'm sure that many probably wouldn't care ), some luck can and should be removed from the game and I think Inconsistent is ok to be removed, even if abilities have never been banned before. Now, I don't think the Inconsistent users themselves should be banned do to most of them being pretty poor pokémon in general (Though, Bibarel's an awesome 'mon ) and there really not being any problems with the 'mons themselves outside of Inconsistent.
Everything else seems fine for now... Either that, or I don't really have an unbiased opinion 'bout 'em. Note that I have only been playing off and on for the past couple of days and that I'm not the best of players in general, I just figured that I'd share my opinion on things while I still had the chance :)