Alright, have quite a bit of experience with most of these mons, so here goes:
Alomomola: One of the most important defensive Pokemon the tier has. Alomomola is essential for many balance and stall teams to keep the likes of Diancie, Mega Steelix, Bronzong, and Druddigon alive. Add to this the bulky offensive mons like Escavalier, Mega Abomasnow, and Scrafty that it can keep alive to let them play more aggressively. Alomomola has a pretty big weakness to Mega (and normal) Abomasnow, Venusaur, and Virizion, but a lot of the fish's best teammates can at least check these threats and can be kept alive to reliably keep checking these threats over the course of the match. The biggest selling point for Mola is the ability to beat Sharpedo regardless of the set. Combine its ability to keep strong Pokemon defensively and offensively alive along with the fact it can beat Sharpedo rather reliably, and Alomomola deserves S rank imo. It also soft checks just about any physical attacker that can't hit it for super effective damage.
Scrafty: Scrafty I feel is fine where it's at. That being said, I don't think Scrafty should be ranked for its DD set anymore. With LO Accelgor, Aerodactyl, Scarf Durant, and plenty of RU's wallbreakers either being faster than Scrafty after DD or simply having very powerful moves to deter Scrafty from setting up, I don't feel DD is as effective as it was. Personally, I've been using a bulky Choice Band set that acts as an offensive pivot into most physical attackers with Intimidate and decent HP investment. Most notably, it provides an offensive check to stuff like Tyrantrum, Mega Steelix, Flygon, and Rhyperior while posing an immediate threat with STAB Knock Off or High Jump Kick. It's a solid holepuncher and pivot into a lot of physical attackers that works well on plenty of balance and more offensive teams. No way it should drop all the way to B rank. B+ maybe, but I think it's fine in A- rank.
Sigilyph: I think Sigilyph is fine where it's at. It has a pretty bad case of 4MSS with Energy Ball, Dazzling Gleam, and Dark Pulse all having their uses and the inclusion of Hoopa in the tier makes it all the harder for Sigilyph to pick as Dark Pulse has newfound use for not only Hoopa, but also Meloetta. It's still a very good Pokemon and underrated Special Attacker, but it certainly has issues with 4MSS more than it ever has before which keep it from being quite as reliable as you'd like an A+ rank Pokemon to be imo. That and the rise of Pursuit users due to Hoopa indirectly hurts Sigilyph. It's good in A rank.
Sneasel: Sneasel is a very solid cleaner and revenge killer in this meta. Having access to Ice Shard and Pursuit makes it a fantastic offensive utility Pokemon. Being able to pick off Flygon and Tyrantrum while Pursuit trapping Hoopa, Meloetta, and Sigilyph is really cool for an offensive mon. High Speed and solid STABs in Icicle Crash and Knock Off allows it to clean pretty reliably as well. Dark + Ice isn't easy to wall either, which can let it chip down many defensive Pokemon in the tier. Overall, Sneasel is good enough for A rank due to a great STAB combination and utility between the fastest priority and Pursuit in the tier.
Aerodactyl: Aerodactyl thrives in a more fast-paced metagame which is generally the one we have now. The problem lies in a few things. First of all, Aerodactyl struggles with common defensive Pokemon in the tier. Alomomola stops it no questions asked and Mega Steelix, Rhyperior, and Tangrowth are more than capable of taking a couple of super effective EQs and Aerial Aces respectively. What's worse is that Aerodactyl's decent defensive typing doesn't have a chance to shine in a tier where Fire- and Ground-types commonly have coverage or secondary STABs to crush Aero. And finally, the most common Scarf users in the tier can generally switch into a move or two from Aerodactyl. Tyrantrum, Medicham, and Flygon can all handle Stone Edge with the latter also being immune to EQ. Less common Scarfers like Durant and Meloetta can take a single move on switch-in to revenge kill Aerodactyl or simply wait until after a KO to catch Aero off-guard. I think a drop to A- rank is warranted due to its less-than-stellar matchup against many of the tier's top threats.
Escavalier: Escavalier's ability to handle Mega Abomasnow, Pursuit trap dangerous Psychic-types, and / or wear down Steel-types is really useful in this meta. Pursuit has generally become better than Drill Run due to the influx of Hoopa and Meloetta. As long as Mega Abomasnow is still in the tier and there are powerful Psychic- and Ghost-types to Pursuit traps or Steel-types to weaken, Escavalier has a place in A- rank.
Slowking: Slowking is still a very solid Pokemon, but it suffers from a meta that is quite hostile to it. Hoopa is a powerful wallbreaker that has dropped that simply doesn't care about the prospect of switching into Slowking. Mega Abomasnow and Sharpedo also cause Slowking plenty of problems between Giga Drain and Dark Pulse respectively. While Sharpedo is frail and Mega Abomasnow is very weak to Fire Blast, it's still a nuisance for Slowking to not reliably use its STAB moves when these major threats are present. The rise of Pursuit trappers doesn't really help as it's generally forced to use Colbur Berry to ensure it doesn't instantly drop to Pursuit when it tries to switch to activate Regenerator. Dropping Slowking to A- rank is fine at this point. Still pretty solid, but has more issues than it probably has ever had in RU since BW2 gave it Regenerator.
Tangrowth: Who could have imagined the addition of one Pokemon would change so many things for Tangrowth. But that is what has happened to it with the introduction of Venusaur. Venusaur's Speed, higher special bulk, and STAB Sludge Bomb just makes offensive Tangrowth hard to justify on most teams. It's made worse by the fact that Venusaur has little to no issues switching into Tangrowth and can blow it away with Sludge Bomb. I would say Tangrowth should drop to B+, but I think it still has enough between its Life Orb and AV sets to stay up in the A ranks. AV sets keep decent offensive pressure, gain the ability to check Sharpedo and Manectric pretty reliably due to the heightened special bulk. A- rank seems fine for it. Still pretty good, but hard to use over Venusaur now.
Manectric: A defensive core without Diancie is generally vulnerable to Manectric. Electric + Fire coverage is very potent in a tier where many teams like using Mega Steelix / Bronzong + Alomomola / Blastoise + random Grass-type cores. Manectric's only drawback is its reliance on Hidden Power for coverage. Even then, you can use that to your advantage and save the Hidden Power type until the right target comes in. Life Orb is the best set by far, but it is a Scarf user that can outspeed most other Scarf users with that high Speed tier. Scarf sets work a lot like Rotom-C used to work and Life Orb sets are basically a slightly slower, but better version of Jolteon. I think A rank is warranted due to its strong matchup against most defensive cores and ability to maintain usefulness vs. offense with one set.
Amoonguss: Amoonguss is in a very interesting position. Fighting-type usage is at an all-time low it feels like, which may seem to hurt Amoonguss, but actually helps it. In this meta, Amoonguss is counted on to handle a lot of special attackers, like Sharpedo, Manectric, and Venusaur. With Virizion being the only common Fighting-type (top 25 mons overall) that Amoonguss has a favorable matchup against it can afford to shift some Defense EVs to Special Defense to give it a much better chance to handle super effective / neutral STAB coverage from Shark, Mane, and Saur. B+ rank seems fine for it.
