My opinion on Roserade = S: Agreed (To an extent)
I think that Roserade is worthy of the S rank due to its solidified offensive presence that allows it to punch through many different pokemon without ANY difficulty. It even punches right through Mega Blastoise and Milotic like nobody's business. The stereotype of "great offenses but low defenses" DOES NOT APPLY to it. Its respectable special defense allows it to sponge up some special hits and prepare to retaliate back with super-effective coverage. Although its physical bulk is not what I wanted, overall, it has decent stats across the board. However, let me just say that its HP and physical defenses aren't good. Pretty much anything that has a powerful physical attack stat or can pack a strong physical hit decimates this thing, and a Grass-Poison typing sounds good on paper, but sadly, Grass is an easily exploitable typing. In fact, Roserade is reliant on Life Orb to do damage, and that thing CHIPS AWAY AT YOUR HP VERY FAST. Pretty much any specially defensive wall can tank this thing and because Roserade's strongest STAB move, Leaf Storm also eats away at your special attack, it just ends up "beating a dead horse". Even those resisted or neutral hits will hurt a lot, even with Roserade's decent special bulk. Overall, let me just say, Roserade should stay in S, but in the next VR update, I think there needs to be an S- rank.
Barabarcle = A-: 100% AGREED AND I WILL NOT SAY ANYTHING ELSE.
The main problem with the collectible pokemon is its... typing. Water/Rock sounds good on paper, until you realize HOW COMMON SHAYMIN AND ROSERADE ARE. Barbaracle HATES Grass-Types, having a QUAD weakness to any grass-type pokemon. And They. Are. Grass. Types. Really, it can be dangerous for unprepared teams, but honestly, more and more and more and more and more teams just prepare for this guy. Really, it is vulnerable to being pressured aggressively from pokemon such as Virizion, Bewear, and Zygarde-10%. Shell Smash somewhat alleviates this, but because it also lowers defense and special defense, what is its greatest strength is also its greatest weakness. Heck, Shell Smash just makes it more vulnerable to being KO'ed while also making it stronger and faster. I think A- sounds representative of it for now.
Yanmega = B: 100% DEFINITELY AND AGAIN, I AM NOT GOING TO SAY ANYTHING ELSE AND THIS IS FINAL. AND I MEAN IT. DON'T TAKE THIS LIGHTLY.
Honestly, its speed is terrible. "YEAH. SPEED BOOST HELPS WITH THIS" is what many of you are going to say. That's right, but considering how bad its defenses are, especially on the special side, honestly, at this point, Speed Boost doesn't even matter. Tinted Lens is useful, but pokemon such as Moltres just decimate this thing. LOOK AT THIS GUY'S DEFENSIVE TYPING. Bug/Flying is just pure bad. A quad weakness to Stealth Rock means that Yanmega will probably die upon switching in (Unless you have Mega Blastoise). Choice Specs can give it better matchups against Steel-Types, but by then, Yanmega will most likely be so badly crippled that they'll just KO it before it has a chance to do anything else.
Slowking = B: No Comment
I'm not exactly sure about this, Slowking in B+ doesn't sound generous to me anyways.
Swellow = B+: STRONGLY DISAGREE
Let me just say I disagree with Swellow rising to B+ and I think it should drop to B- or even C+. Why? LET. ME. EXPLAIN. NOW. Its bulk is even worse than Mega Absol's. 60/60/50 bulk is just terrible. Its really only decent stat is its speed, and even then, its offenses are just depressing to see. Scrappy Boomburst is useful for taking care of those pesky Choice Scarf and Priority users, but there are much better answers to those. It's so reliant on Choice Specs that pretty much any Knock Off user can just go in and literally cripple the life out of Swellow. If you read my explanation about my opinion on Roserade rising to S, the same thing applies here: any specially defensive wall can just tank anything Swellow tries to throw at it and prepare to hit back hard. U-Turn can alleviate this issue to an extent, but there are already a lot of pokemon which can cripple or fatally KO Swellow.
Drapion to A-: Meh
I really don't think Drapion is really THAT good to be deservant in A-. 90 for a physical attack sounds rather passive, don't you think? Without Choice Band or Z-Crystals, it isn't good at being a sweeper or wallbreaker. It does sport a good speed stat, which somewhat alleviates this issue, but you know who else has a good speed stat? Honchkrow, and look where it's ranked. Now, Honchkrow doesn't have a good defensive typing and suffers a lot from its pitful defenses, which Drapion doesn't struggle with, but even then, Honchkrow is simply put, easier to fit on a team than this Ogre Scorpion thingy. While the high power of some of its coverage moves alleviates its passivity, there are a lot of special sweepers/wallbreakers that can take advantage of Drapion's lower special defense.
Sigilyph rising: No comment
Eh, I think Sigilyph is fine where it is, but for now, I'll just say that I could possibly see it rising in the future.
Feraligatr to B-: No comment
Yeah, Barbaracle's typing is worse than Feraligatr, and Barabaracle loathes grass-types more than Feraligatr does. I'll just say that Feraligatr is fine where it is, no need to drop it.
Now time for my own suggestions:
Add Mega Absol to the rankings:
I won't specify on exact rank due to how long this post is, but let me just say this: RUBL=UU. Sounds weird, right? However, let me say this: the upper tiers aren't a place for Mega Absol. Its subpar defenses are just pure bad, and honestly, that damage can rack up very fast. Its great offenses can somewhat alleviate this issue, but it's so glaring and so bad that Mega Absol doesn't do that well in its current tier like it did back in the days of ORAS. Now, I know that performance in an upper tier won't make them added again, but these are just suggestions.