Durant is not S rank at all and the arguments for it are extremely exaggerated / terrible.
Let's look at the Hone Claws set. Durant needs all three of its standard attacks (Iron Head / X-Scissor / Superpower) to function at its best. The problem with saving "but Qwilfish and Jellicent are not checks because of Thunder Fang!!!" is that a when making an assertion like this, many fail to understand that by dropping one of Durant's other attacks in favor of the significantly less optimal Thunder Fang, Durant still has to pay the price of dropping a bit of its effectiveness as a result. For instance, dropping X-Scissor makes Tangrowth, Twave Uxie, and even certain Bronzong decent checks to Durant itself in exchange for being able to cut through Qwilfish / Alomomola. Durant can't just run Thunder Fang over one of its standard moves and not lose a bit of effectiveness as a result. It will always have something that can hard / wall check it. Even outside of the defensive spectrum of handling Durant's attacks, Durant can really only set up on very specific attacks (think Leaf Storms) or by forcing a switch. It's an incredibly frail Pokemon which only offers defensive synergy in the form of checking Mega Glalie on offense. Second, let's say you ended up getting that Hone Claws boost, you're still forcing a one-for-one considering practically any Choice Scarf user can revenge the thing, so in exchange for getting one kill, you're either being forced out and thus lose a ton of momentum or Durant is going down the following turn.
The problems for this set boil down to:
-Difficulty setting up
-Difficulty keeping a sweep
-Always having a handful of solid defensive responses no matter what it does
This is not S rank because it requires way too much support and has a number of significant flaws.
Let's look at the Choice Scarf set.
Because Durant is being nominated for S rank, it's fair to compare it to another S rank Choice Scarf user, Tyrantrum. Unlike Tyrantrum, Durant does not have an extremely spammable STAB, its STABs also have poor coverage in comparison and in general. The raw power of Tyrantrum's Head Smash allows it to pose as a threat to even defensive cores / Pokemon, something that Durant cannot do. I'm not saying that a Choice Scarf user should be able to put in work vs defensive teams, but what makes Tyrantrum such a good Choice Scarf user, and what sets it apart from the others, is that it can do just that simply with the threat of a single attack. This is the key thing that distinguishes Tyrantrum from the other Choice Scarf users in RU and what helped get it into S rank in the first place. In comparison to even Choice Scarf Delphox which can cripple defensive threats with Switcheroo, Scarf Durant is practically useless vs bulky water + Steel core which you will find on practically any balance / stall. An S rank threat should never be useless or a liability.
Now let's talk about the other glaring flaw with Choice Scarf Durant, that being, having to rely on a 80% accurate moves to revenge kill certain Pokemon. You should never be playing against Durant hoping it will miss, just like you wouldn't with Moltres in the past or Tyrantrum now. That's a given. However, unlike the previous two Pokemon and even other Choice Scarf users now such as Delphox, Durant does not have an accurate coverage move / STAB to fall back on. Not having something accurate to fall back on is a pretty big hit on its viability. Whenever I'm relying on Durant to revenge kill Venomoth / Scrafty, I have to cross my fingers every time and hope that it doesn't miss because if it does, I lose. I don't have to get into that same guessing game when I'm using something like Choice Scarf Delphox. With a Pokemon like that, it can revenge kill various set up sweepers with accurate moves that gives me a huge sense of security. Even with Tyrantrum and Moltres, while true they had to rely on inaccurate attacks every now and then, they had/have accurate STABs/moves to fall back on when needed. You will come across a point where Choice Scarf Durant will miss and it will cost you the game, and a lot of the time, you had no other choice but to go for the inaccurate attacks. Other S rank Choice Scarf users now and then don't have those flaws.
In short, Choice Scarf Durant:
-Will not put in work vs your bog standard balance / stall core in anyway, no Trick/Switcheroo, lack of raw power/STAB, nothing will help it put in the work, making it a liability in those matchups.
-Choice Scarf Durant can be unreliable as a result of having to rely on Hustle to be a proficient Choice Scarf user
Please don't argue saying you don't have to use Hustle on Choice Scarf because you do. Its STAB combo and move BP is already unimpressive as is, but without the Hustle boost, it's unbelievably pathetic in regards to its damage output.
This is not S rank.
The other sets, All-out Attacker / SubPass, I won't get into, but I don't think I need to explain why those sets are not S rank worthy, especially due to the fact that those two sets weren't even being acknowledged to move Durant up by those who nominated it / pushed for it to be S rank in the first place.