Durant is really interesting honestly. It's kind of odd that before the recent changes in the last 2 or 3 months, Durant was always Durant and wasn't really viewed on the same pedestal that it is now. I don't know, maybe it's just me. I think that the most dangerous durant set falls on either the Life Orb Attacker or the Choice Band set. That doesn't say anything about the scarf set nor the hone claws set, both of which are powerful in their own right. But with a Life Orb, switching into Durant is really difficult, especially during the middle stages of the battle. Once everything has taken some damage, countering LO Durant means that you will take a big hit, even if you resist. Here's an example:
Let's use something really defensive... Say... The Great Wall of Mola (Alomomola). For the sake of argument, the early phase of the battle has transitioned to mid-game phase, a few shots have been fired, and 1, 2, or 3 mons on each side have taken "minor" damage; no KOs yet. Let's say Mola is used as a counter and comes in on rocks and it's now sitting somewhere between 76 and 88% HP before it takes the hit (A good scenario for Alomomola to be used as a counter in general). Here are the theoretical outcomes for LO Durant and standard Mola hard switching into its move:
(1) 252 Atk Life Orb Hustle Durant Iron Head vs. 120 HP / 136+ Def Alomomola: 105-125 (20.9 - 24.9%) --
Given the good scenario for Mola, Durant will dish out 20.9 - 24.9 percent. At the end of the turn (after leftovers), Mola should have between 58% HP and 74% HP
So this is the best scenario for Mola other than Durant Missing its mark because thunder fang will do at most 53.8% to Mola after the first hit, meaning Mola can use wish or whatever.
(2) 252 Atk Life Orb Hustle Durant Superpower vs. 120 HP / 136+ Def Alomomola: 211-248 (42.1 - 49.5%) --
At the end of the turn in this case (after leftovers), Mola should have between 33% HP and 52% HP. Now... This is still a good situation for Mola because Superpower removes the attack boost granted by Hustle essentially (but not the accuracy drop ^.^). Even at the absolute worst scenario where Mola is at 33% after hard switching, Mola can still survive; however... -1 252 Atk Life Orb Hustle Durant Thunder Fang vs. 120 HP / 136+ Def Alomomola: 153-182 (30.5 - 36.3%) Basically forcing Mola to hit protect for an extra leftovers turn or switch out. Regardless of where this scenario stands though, Mola has had a fair chunk of health ripped out of it. Even if it comes in later after Regen (rocks are still up assumedly), after rocks Mola will have 73% HP in the very best scenario, which is not necessarily bad for Mola, though, I would have to use Mola with a bit more caution in regards to hard switching. Overall though, Mola is relatively okay after this.
(3) 252 Atk Life Orb Hustle Durant Thunder Fang vs. 120 HP / 136+ Def Alomomola: 229-270 (45.7 - 53.8%) -- 94.1% chance to 2HKO after Stealth Rock and Leftovers recovery ... Ouch... So... Uhm... Yeah... If your opponent makes a good prediction and Mola takes a Thunder Fang, Mola will probably have to run away. Now of course, you do have protect + leftovers if you seriously need it (and have leftovers over rocky helmet). So it isn't impossible to stay in, but if you did that, then you could be taking a risk depending on what the opponent does. This also leaves you prone to losing momentum. Also, I want to point out that for this specific outcome Alomomola is starting from full HP. If Alomomola is not starting from full HP (before stealth rocks) as it comes in to take a hit, there is a significantly higher chance that Mola cannot stay in as the starting HP before taking the hit decreases...
(4) 252 Atk Life Orb Hustle Durant X-Scissor vs. 120 HP / 136+ Def Alomomola: 211-250 (42.1 - 49.9%) -- 27.3% chance to 2HKO after Stealth Rock and Leftovers recovery ...This is also not a particularly good scenario for Mola because if we are in the good scenario where Mola is sitting between 76 and 88% HP after taking rock damage and before taking Durant's attack, at the end of the turn (after leftovers recovery) Alomomola should have between 33% HP and 52% HP remaining... There is a decent chance that Durant can get the KO with Thunder Fang next turn. Even if you choose to gain an extra 6% from leftovers through protect, Durant would still have a chance to get the KO with Thunder Fang. This is Standard Alomomola (120 HP, 136 Def, 252 SpD, Bold Nature).
All that this proves is that Durant has the power to seriously keep Alomomola from acting as a hard counter for 2 moves with just a life orb essentially. That's not a very easy reality to achieve.
If we are talking about Choice Band Durant, then we reach a new level of complexity entirely. If we have LO Durant and spikes are thrown into the equation, you have something that is virtually non-counterable. Thunder Fang will have 76% accuracy thanks to Hustle, which at the very least gives some amount of fairness for dealing with Durant; unfortunately, 76% or 80% are still accurate enough to make Durant a terrifying foe to face. Durant is such a huge threat in RU that any team lacking proper preparation for it will be considered a borderline non-viable team. By proper preparation, I mean that there should be an answer to at least 2 different common Durant sets. For instance, I had a pretty good balanced offense team that I was laddering with several weeks ago (I was around the 1400s). That team did get an rmt if you're interested, but that aside... That team had 2 ways of dealing with Durant. Scarfed Tyrantrum could revenge kill the LO variant with Head Smash. Diancie/Steelix could act as a soft check to the choice variants depending on the move used. But this was the problem my team had with Durant... I had no way of countering Durant, which made it very unpleasant to deal with. There was only 1 answer to the Hone Claws Variant and Scarfed Tyrantrum's Head Smash was rarely powerful enough to revenge kill Durant after rocks. If the only answers I had to the scarfed variant are soft checks, then they usually ended up costing me momentum or made it impossible to stop Durant from coming in, getting a kill, then leaving. The same with the banded variant. It was also very hard to tell whether Durant was choiced or not because it just outspeeds so many things already and does enough damage in the mid-late stages of battle that distinguishing a choice band variant from hone claws or e-belt or whatever else was essentially impossible to do. So when I say "proper preparation," I mean you have to be able to properly deal with at least the Hone Claws variant in addition to the choice band/scarf or LO variant, otherwise your team will face some problems from Durant. Period. I understand that you have to have 1 method of dealing with Tyrantrum at the bear minimum; yet, Durant somehow needs to have multiple answers. Just because you might have a way of dealing with the Hone Claws variant does not mean you have a way of beating the LO variant, as I hypothetically examined with Alomomola above. You might have an answer to LO Durant, such as Scarf Tyrantrum to revenge kill, but that does not mean you have an answer to the scarfed variant nor the Hone Claws Variant, as I explained with the team I was using a few weeks ago. I advise that you evaluate Durant in the same manner as I tried to with the Alomomola example before reaching a conclusion about it. There are quite a few more than just Alomomola that turns into a slight weakness due to Durant's incredible strength. I'm leaning more towards a ban here.