Building on what I already mentiond earlier, I would like to add a few things. First of all, Moltres is certainly rather restrictive when it comes to teambuilding. Life Orb Molt only has three decent switchins in Aerodactyl, Slowking, and Lanturn. To make matters worse, Aero takes 50-60 from LO Fire Blast and Hurricane, and it dies on the follow up turn if it attempts to Roost. As for Slowking, it is 2hkod by LO Hurricane after SR and always 2hkod by Specs Molt. Lanturn is arguably the best Molt switchin but it does not do much beyond switching into Molt, Manectric, and Rotom-N. Hence, Lanturn is generally less useful and much harder to fit. We are thus at a point where the two most common answers to Molt are somewhat shaky, while its best answer does not fill too many functions outside of switching into it. Thankfully, however, we do have additional ways to deal with Molt. For one thing, the hazard control in this tier is rather lackluster, which makes it easier to limit Molt by means of setting up SR. Oftentimes, this means that it will only be necessary to switch into Molt once or twice per game. For this purpose, Aero and Slowking will usually do just fine, granted, of course, Hurricane can do dumb stuff. Furthermore, Moltres can be checked offensively by mons that are faster than it. All they need to do is pack a rock move. For instance, Sceptile can run Hp Rock or Rock Slide, Durant can run Rock Slide or Thunder Fang, Scarf Emboar can run Rock Slide, Sigilyph can run HP Rock, Cryo can run HP Rock, Tauros can run Rock Slide, and so on. In addition to this, many slower mons can be tweaked to check Molt in a 1v1 situation. For instance, Drudd, Golurk, Entei, Regirock, and Piloswine are examples of five common mons who can tank one hit and kill it back with Thunder Punch/Outrage (Drudd) or Stone Edge/Rock Slide (Golurk, Entei, Regirock and Pilo). Granted, specs would indeed kill Drudd and Golurk. Additionally, Uxie can outspeed Molt and 2hko it with Expert Belt Thunderbolt or neutralize it by means of clicking Twave. Hence, while Molt is indeed a pain in the ass when it comes to building, we do have access to lots of counterplay and it tends to be much less broken in practice. However, I would still argue that it ought to be banned for the reason that it tends to make games less competitive by means of introducing lots of RNG.
Durant is a bit different from Moltres. While Molt Life Orb is the most common Molt set, followed by Specs, and then the very rare Scarf; Durant is mostly Scarf, followed by Hone Claws Lum/Life Orb/Fighting Gem, AoA Life Orb, and CB. Scarf Durant is particularly good vs more offensively inclined teams. It outspeeds every other mon in the tier while still packing a decent punch, thus making it a rather potent win con in such match ups. However, Scarf Durant has lots of defensive answers. Qwilfish, Alomomola, Amoongus, Emboar, Steelix, Moltres, Escavalier, and Seismitoad may all switch into it. Furthermore, lots of mons may eat a hut and beat it 1v1. As for non-scarf Ant, its many different sets makes less predictable than Molt. This makes it more difficult to deal with since its checks may vary depending on the set. Despite this, Qwilfish, Alomomola, pdef Amoongus, and Pdef Emboar can still switch into any given Durant. Furthermore, many mons such as Drudd, Golurk, Moltres, and Entei can beat it 1v1. Additionally, certain mons such as Aero, Sceptile, Tauros, Scarf Rotom-N, Scarf Mowtom, and Scarf Emboar outrun and ko it. Moreover, Magneton can also trap it. To make trapping it even easier, you may pair it with Eject Button Amoongus or Alomomola. Another option is to make use of resist berries to check Ant in a 1v1. Tangrowth, Slowking, and Uxie can all run Tanga Berry, which would allow them to live X Scissor and ko it back. Finally, while it is not as weak to SR as Molt, it can be chipped with SR, Spikes, Rocky Helmet, Rough Skin, and Iron Barbs. In other words, while Durant is certainly a phenomenal mon, and while its many sets does indeed make it more difficult to deal with than Molt, we do still have quite a bit of counterplay at our disposal.
With this in mind, can Durant be said to be broken? The RUPL stats which I alluded to in my last post would indicate that Durant is more effective than Molt. One could even argue that having such a high w/l with such high usage would indicate that it is broken. However, if we were to go by this logic, then Cryogonal would be the most broken mon in the tier, followed by Kabutops. I feel confident that nobody would consider any of these to be broken.
Alright, so, from this point, I think one could argue in either direction with regards to whether Ant is broken or not. However, is Ant uncompetitive? Yes, in my opinion it is. With Ant, every single turn is like hitting a Stone Edge. Unless of course you're actually using Stone Edge, Rock Slide, or Thunder Fang, in which case the odds get even worse. Nevertheless, Scarf Swarm notwithstanding, Durant introduces lots of RN and reduces the amount of skill involved significantly. As such, I would argue that it is uncompetitive.
How about we go for some more replays to illustrate my point?
Case 1, BWPL Week 2:
https://replay.pokemonshowdown.com/gen5ru-1401582046-rwbmt8s8qr9aqtgn33p14gzkjjwwi33pw
In this game, both Feli and I have Durant + Qwilfish offense. In theory, Qwilfish should be able to deal with Ant again and again. In practice, however, it went a bit differently. I managed to deal with his Scarf Ant just fine, by means of weakening it with hazards + helmet. However, My Ant was able to make lots of progress vs his team with the help of spikes. Firstly, it managed to weaken Qwilfish with Spikes + Iron head. It then went on to kill Drudd when Qwilfish was too low to switch in. Furthermore, while it seemed perfectly rational for me to be Scarf, my Ant turned out to be bluffing as it was actually Shed Shell Hone Claws. This allowed it to get yet another kill as Feli made the reasonable decision of going Tang to claim a ko. This replay shows how difficult it can be to deal with Ant due to its many sets. It shows how non-choiced Ant, with the help of Spikes, can make progress even vs Qwilfish teams. However, it also shows how easily I dealt with Scarf Ant, despite all my mons being slower and Qwilfish being my only good switchin. All in all, this game probably does not indicate that Ant is broken, but it does show us some of the difficulties with regards to dealing with Ant. Additionally, while it did not come into play, the game very much came down to RNG. If I were to miss my Iron Head vs Drudd or X Scissor vs Tang, then I would die in return.
Case 2, BWPL Week 3:
https://replay.pokemonshowdown.com/gen5ru-1406051837-p57vf1owo9pvsr4fv70byhfdmxqv1fwpw
In this game, Esche has a standard team with Durant while I have a standard team without Durant. Even so, I do not feel particularly disadvantaged. This is because i happen to have both Qwilfish, Emboar and Steelix. Between these three mons, I cover Ant very well defensively. Additionally, both Aero and Sceptile outspeed and ko Ant. In other words, Ant is not really an issue to me at all. Hence, I think this team is a good example of how you can build an offensively inclined team which still has good matchup vs Ant. Based on this game, it would seem completely unreasonable to conclude that Ant is broken.
Case 3, BW Cup Round (3? 4? idk):
https://replay.pokemonshowdown.com/smogtours-gen5ru-474588
In this game, Finch has a Scarf Durant against an offensive team with no hard counter to it. Every single mon of mine is 2hkod my one of Ant's moves. Even so, it turns out fine for me in the end. Meanwhile, my Moltres just goes crazy if it hits its moves. It ohkos every mon and only Ant and Rotom outspeed it, the latter of which gets trapped by my Drudd. In the end, Molt gets 2 kills and some chip on Ant before missing and dying to Qwilfish. This game is a perfect example of how much RNG is involved when Moltres and Hustle Durant are in play. If Molt simply hit Cane vs Qwil, then the game would be over. Instead, it missed, thereby forcing me into a position where I needed to not get crit by Sucker Punch and hit my Iron Head with Ant to win the game. Clearly, the skill involved was heavily reduced. For this reason, I think this is a good example of why the tier would be bettr off without Molt and Ant.
In conclusion, I do not think that Molt and Ant are broken, but I do think that they are both uncompetitive. For this reason, I believe the tier would be better off without both of them.
Tl;dr: Ban Molt and Ant.
On the Druddigon Question: As a sidenote, the final replay also shows how crazy Drudd is. My Drudd gets 2 kills + some chip, while his Drudd gets 2 kills + 90% on Ant. Idk if I will have the time to do a bigger post on Drudd but in my opinion it actually fits the definition of a broken mon. No matter what team you have, irrespective of whether it is offensive or defensive, of what kind if mons you are using, Druddigon is always good. It has the potential to get several kills in every single game. In my opinion, a standard team without Drudd is likely to be at a disadvantage vs a standard team with Drudd. Thus, I think there is a strong argument for banning it. However, I would not mind banning Molt and Ant first before moving on to Drudd.