[alexwolf]

Another awesome offensive counter to Durant, which noone has mentioned yet is Scarf Magneton. Timid Magneton OHKOes 100% of the time with Tbolt without SR and leaves no chance to HC Durant to pass the boosts to a teammate.

So for the HC set we have 3 solid counters, Steelix, Scarf Magneton and Circle Throw Poliwrath, and out of those 3 Magneton can fit on offensive teams, all 3 pokes can fit in balanced teams and Steelix and Poliwrath can fit in stall teams. So every playstyle has at least 1 solid counter for Durant's most dangerous set.

The CB set has those counters: Steelix, Magneton, Gligar. And again there is a poke that can fit in any type of team.

So every single playstyle has has options to counter Durant, especially the HC set, which is the most dangerous.

Now if we wanted to talk about checks the list would be quite big. Any faster pokes that hit from the special spectrum can ohko Durant. Examples are Scarf Moltres, LO and Specs Sceptile, Scarf Galvantula and Manectric, Aerodactyl, scarf Rotom-A, scarf Rotom-C, Accelgor, Archeops, Scarf Typhlosion, Unburden, Hitmonlee and Sharpedo.
Add the fact that as shown by DetroitLolCat, Durant cannot switch-in against most of the top RU pokes, and this means that most often than not Durant will be coming in after something of yours dies and after it kills 1 poke at best it is going to be forced out by any faster special attacker that all ofensive teams should carry.

This means that against offensive teams Durant will pretty much come in after a kill, and after he kills something it is going to be forced out, which means a 1 for 1 trade, except that the other team will be one step ahead.

Against stall teams, Durant will have a hard time breaking through a combination of Steelix, Cofagrigus, Qwilifsh, Gligar, Poliwrath and even Magneton.

The teams that i imagine that will have the biggest problem against Durant are balanced teams, once their check/counter to Durant is worn down/removed. Most balanced teams have only 1 poke faster than Durant, a scarfer most likely, or only 1 counter and no checks, and as said before Durant's counters can be easily worn down without Wish support.
So Durant will be a huge threat for balanced teams, but i don't think it would be so much to the point of being broken, because as shown he has 3 counters and ~12 checks.

And even if it is broken, i don't think that we can know yet for sure. The metagame hasn't yet adapted fully to the new threats, and so some things stand out as too powerful. So let's let the people try to figure out some solutions and if they can't then let's procceed to take actions. But it is too early and since i don't see anyone finding Durant blatantly overpowered, then i think that for now he should stay in RU.

EDIT: I now noticed that i only mentioned offensive checks. If we also take defensive, and by defensive i mean those that can take 1 hit and then kill back or cripple, then Entei, Cofagrigus, non choiced Moltres, Aggron and non choiced Rotom also come into play.