I know many of you might not agree, but I think there should be two suspects:
Exadril/Doryuuzu
Completely overpowered, and its set is pretty much known to all as Swords Dance/Earthquake/Rock Slide/Filler with a balloon. There are only a handful of decent switch ins after a Swords Dance (Skarmory, Gliscor, ect) and the latter can't do anything until the balloon is popped. Immune to both T-Wave and Toxic, and unbeatable in the sand. Perhaps most of this is due to the SS or Drizzle ban, but on pokemon online (which does not have this ban) it is an absolute house, and I have lost counts to the amount of 4-6/0 sweeps I've gotten. Most of the teams are sand, and the only sand teams I've seen that don't run dory run Randorosu (he is not that common though). Priority moves such as Azumaril aqua jet or infernape mach punch, ect can deal with it, but they cannot switch into an earthquake. And they can both be absorbed by my second suspect:
I do not mean to rant, and although I don't have specific calcs, I would take a minute for you to realize how much the metagame rotates around these two. For dory, I think his fate may depend on how the rain neutering goes (I feel if SS and drizzle were both legal, Dory would be fine), but I do believe latios is too good for this OU.
While I agree that Latios is absoluteley too powerful fo OU, Doryuuzu is a different story (Randorusu is the bigger concern, but anyways...)
The problem with Doryuuzu is the inconvenience of it, not it's power. It has several "counters", so-to-speak, but they can't really switch in (the ones that are offensive/carry priority. The rest shall come later). I, however, have been playing with Doryuuzu in my SS Team (look, I've been playing with sand since early 4th Gen, I just enjoy my playing style, deal with it), for a while now, and I have to say that it isn't broken. A massive power house? Yes. A prominent threat? Of course? Hard to beat? Arquable, but is that not one of the goals of battling? To be challenged and to adapt to your surroundings? Well, it isn't easy, but quite manageable. Skarmory and Hippowdon are quite reliable and can phaze him out, while Hippowdon can KO him with EQ, and Skarmory is immune to his precious STAB and can phaze him around with Whirlwind. Gliscor and
Unaware Quagsire also stop him cold, while the former has the typing to easily wall is common attacking set and able to eliminate it with EQ, Ice Fang, etc, and the latter has no problem switching in when it's at +6 and can boost it's own defenses, hit hard with Waterfall / Earthquake, and can easily pivot back with Recover. Dory also falls if you have some hazards, Mach Punch/Vaccum Wave/Aqua Jet, a burn, etc. And you know what's nice? All of these counters are good, usuable, OU pokemon that can serve many potential roles INCLUDING this one.
If anything, as already stated, Latios needs to go (and hopefully Randorusu can see some looking into).
Edit: Just saw this. The game doesn't rotate around these. It rotates around Tyranitar, Hippowdon, Ninetales, Politoed, Abomasnow, Roobushin, Shanderra, etc. I swear I always see at least one of these on every team.