Raikou: Abstaining, therefore not writing a paragraph
Froslass: I believe Froslass to be BL under the Support Characteristic. Firstly, we will defined the Support Characteristic, by Smogon, to the "If a Pokemon can consistently create an environment for which a teammate can sweep a significant portion of the opponent's team, then it is BL/Uber". To make this clearer, I will say that the Pokemon can only be BL if that piece of Support is the only thing holding a sweeper from outrightly broken. Back to Froslass, her effectiveness in UU can be compared to the effectiveness of Deoxys-S in Ubers, where unless the opponent runs a designated anti-lead, Froslass will get 2-3 layers of Spikes up most of the time. Coupled with the ability to not see those Spikes getting Spun away in her face, those Spikes are likely to stay for a big part of the match. This is what sets Froslass apart from any other Spikes user, be it Cloyster, Omastar, Glalie, etc. Froslass is also the fastest out of the UU Spikers, and with access to Taunt, can shut down many other leads at the same time. Those faster than Froslass (With the exception of Sneasel), are 2HKO'd if they ever dare to Taunt her. Examples of this include Ambipom and Alakazam. This is not mentioning the fact that Froslass can also run a bulky Spiker set that can beat most Spinners, meaning that 2 or 3 layers of Spikes will be there to chip away the health of opposing Pokemon for the remainder of the match.
So, enough on why Froslass is an excellent (too excellent) Spiker, now to explain why Spikes make sweepers broken, because that is what the Support Characteristic is trying to scrutinise. The best example to show this is the example of Registeel. Registeel is one of the best walls in UU, being able to take most attacks and being able to paralyse it with Thunder Wave. It is genearally able to defeat Raikou should its health be over 75%, and anything under would be shaky. However, if the Raikou user's team has 2 layers of Spikes up (Which is usually quite easy to achieve with Froslass), and does stuff like double switching out knowing Registeel would come in and immediately threaten out, only to bring Raikou in again later, the Registeel would be at 62.5%, which is now within a 2HKO range for Life Orb Raikou's Thunderbolt (LO Timid Raikou's Thunderbolt does 29.12% - 34.62%). Another great example would be Moltres. With just 2 layers of Spikes, Modest Life Orb Moltres can guarantee a 2HKO to standard Milotic with Air Slash + Hidden Power Grass (Air Slash does 35.79% - 42.13%, while HP Grass does 44.67% - 52.79%), something that would not be as easy to achieve should Cloyster or Qwilfish or other UU Spikers be in the same position as Froslass. Such damage calculations show that two layers of Spikes allow sweepers to muscle past its designated counters. Froslass can do this much more easily than other UU Spikers, and her typing prevents those Spikes from being spun away easily. This is why Froslass is BL.
Moltres:
I believe Moltres to be UU. To do this, it is best to show that it does not fit in any of the three Characteristic of an Uber, Offensive, Defensive and Support.
The Offensive Characteristic is defined by Smogon to be "Being able to sweep a significant portion of a team with little to no effort under common battle conditions". My interpretation of "being able to sweep a significant portion of a team" is that the Pokemon can come in at any point in the game (As long as it comes in on something that's relatively safe for it), be it early, mid or late game, set-up ONCE, and KO 2-3 Pokemon after setup (2 Pokemon if its late game). "Little to no effort" is usually indicated by how much support said Pokemon requires to carry out the sweep. I will assume "Common battle conditions" in UU to be no weather effect or other field effects like Trick Room, Tailwind and Gravity are up, Stealth Rock is up and no Screens (Reflect, Light Screen) are up. In these conditions, I do not believe that Moltres to fit the Offensive Characteristic. First of all, if Moltres is to sweep, the premier wall of UU, Chansey, must be removed, or Stealth Rock and 3 layers of Spikes need to be up for Moltres to come even close to 2HKOing Chansey with Fire Blast. Secondly, if only Stealth Rock is up, Moltres has no business fighting against bulky Waters like Milotic and Slowking, and the only of way getting past them is if 2 or more layers of Spikes (Or SR and more than one layer of Spikes) are up. Moltres can also get past bulky Waters by running a Sunnybeaming set, but that would severely cut into its type coverage. Thirdly, should Stealth Rock be up on Moltres' side, it would lose 50% upon switch-in, already hampering its sweep before it has started. Lastly, although its Speed is reasonably good for UU standards, it is still not good enough to be sweeping a significant portion of teams. Faster Pokemon like Mismagius, Raikou, Dugtrio, Swellow, Rotom and Miltank are all perfectly capable of coming in and revenge killing it or simply forcing it out. If Stealth Rock is up (Which is commonly is), Moltres would have effectively lost 50% of its HP. Due to this, in order for Moltres to sweep effectively, it requires: 1) A Rapid Spinner to remove Stealth Rock 2) Chansey and bulky Waters to be removed 3) A layer of Stealth Rock and Spikes or 2 layers of Spikes and 4) Pokemon with higher than Base 90 Speed that can revenge Moltres to be removed. That, in my opinion, is way too much support for Moltres to be banned under the Offensive Characteristic.
The Defensive Characteristic is defined by Smogon to be "Being able to wall a significant portion of the metagame with little to no effort under common battle conditions". My interpretation of "a significant portion of the metagame" would be a simple majority, >50%. Although Moltres can run a rather annoying Stall set using Flamethrower/Substitute/Roost/Toxic, it isn't able to wall the metagame unless it is safely behind a Substitute. Most of the time, Moltres would be able to force a Pokemon, set up a Substitute, and Toxic the incoming Pokemon (Usually a bulky Water) before its Substitute is broken. While Moltres can Substitute a few more times to allow Toxic damage to accumulate on the opponent, most of the time Moltres would be forced out before the opposing Pokemon faints. If Stealth Rock is up, Moltres cannot switch back in (Otherwise its stall would have been very short should it have switched out at above 50% HP). Moltres also needs other conditions for it to stall efficiently. Toxic Spikes is very important to any SubRoost staller, and unfortunately, they aren't as viable in UU due to the number of good grounded Poison types (Venusaur being the most obvious) who can come in and absorb them. Simply put, Moltres is not able to wall most of the metagame, therefore should not be banned under the Defensive Characteristic.
The Support Characteristic is defined by Smogon to be "Being consistently able to create a condition in where a teammate can sweep". This includes creating a condition such as Rain and Sun, entry hazards, free setup, or simply being able to repeatedly punch big holes into an opposing team so a teammate can clean up later. I do not believe Moltres to fit the Support Characteristic even though it can punch holes into a team easily due to power of its attacks, it itself requires a ton of Support to do its job already (See Offensive Characteristic arguments). This would mean that unless all of those Support conditions are met, Moltres is not going to be able to consistently setup situations for a teammate frankly because of the support it needs itself. Moltres does not have access to supporting moves like Heal Bell, Wish or anything like that either, so it cannot support the team in a game-breaking fashion in that area either.
Moltres does not fit either of the Characteristics of an Uber, therefore I will vote Moltres to be UU.
Dugtrio:
I believe Dugtrio to be UU. Again, we must look at the three Characteristics of an Uber.
Offensive Characteristic: Dugtrio does not fit the Offensive Characteristic, because it is not going to be sweeping a team. Base 80 Attack is usable with its ability, but it is definitely not anything special. Even with a Choice Band, it fails to OHKO a full health Registeel. It can use its very good Base 120 Speed to be a reasonable late-game cleaner, but this is provided everything faster than it (Swellow and Choice Scarfers), priority have been removed and defensive Pokemon have all been weaken. This is definitely way too much support for Dugtrio to banned under the Offensive Characteristic.
Defensive Characterisitc: Dugtrio obviously does not fit the Defensive Characteristic with its pathetic defenses resembling somewhat like Deoxys-A (Although not THAT bad). Pretty much any attack will at the worst 2HKO it (Iron Head from Registeel, one of the weakest physical attacks, does over 70% to Dugtrio). Even Seismic Toss 2HKOs after Stealth Rock. Dugtrio would be one of the last Pokemon to be banned under the Defensive Characteristic.
Support Characteristic: Here is where Dugtrio's "brokenness" is called into question. Dugtrio is able to trap and kill Chansey and Registeel without much problem (Chansey with Beat Up and Registeel with Earthquake) using its near-unique ability Arena Trap, freeing up a sweep for dangerous sweepers like Moltres and Raikou. However, I would like to point out that although Dugtrio can use its ability to remove these threats, it still will not be able to consistently create conditions for such teammates to sweep. This is because most teams would be able to use another Pokemon as a secondary check to these sweepers. For example, in the example of Moltres, Dugtrio eliminates Chansey. There is no reason why the Chansey user wouldn't pack a bulky Water alongside Chansey (Bulky Waters have become integral parts of most teams in any metagame anyway). Raikou is another example. Dugtrio can remove or severely injure Registeel so Raikou can sweep past it. However, there are still other checks for Raikou that a player can easily run. Torterra can stop all non-HP Ice Raikou, Steelix all non-HP Water Raikou and so on. All of these Pokemon are quite common in the UU metagame. Dugtrio might have remove one check (And it will not be so easy to remove the other one, either because Dugtrio would be unable to, due to their bulk, or the opposing is now alerted to Dugtrio's presence and will be more protective of their Moltres/Raikou/Sweeper's checks) but not the others. What's worse, Pokemon like Chansey can easily run Shed Shell if Dugtrio becomes so prevalent that it becomes necessary to do so. So yes, while Dugtrio can make the job of a fellow sweeper easier, it is usually not easy enough for Dugtrio can be banned under the Support Characteristic. Another aspect is that since Dugtrio needs to power of Choice Band to be anywhere near efficient, it would usually become locked into a move which can be setup fodder for an opposing sweeper. A Pokemon like Torterra (And many, many, others) can easily come in on Dugtrio and set up Rock Polish and proceed to sweep should its counters be removed. In this case, it is absolutely irrelevant that Raikou or Moltres' counters have been removed, since they are going to be swept anyway. Dugtrio's usefulness in trapping and taking out counters must be weighed up against its liability to the user (And this liability can be very weighted), and this is usually not enough to ban Dugtrio under the Support Characteristic.
Dugtrio does not fit any of the Characteristics of an Uber, therefore I will be voting Dugtrio to be UU.