Disagree with dropping Shaymin-Sky to B. If you look at the B mons they are for the most part outclassed or have severe issues holding them back due to popular trends in the metagame. Palkia is mostly outdone by the Latis bar having better coverage and can't even check Ogre anymore due to getting simply overwhelmed by Primal Kyogre's superior stats; Zekrom suffers from unfortunate dual STABs in a metagame dominated by P-Don and Xerneas (the former of which eats Outrages for lunch despite not resisting); regular Groudon sure has some unique niches but lol have fun not using P-Don, Rachi is pretty bad and as previously stated should be dropped due to simply losing to too many of the common Pokemon (Ekiller, Darkrai, P-Don, P-Ogre, Ho-oh, EQ Mence etc); Khan suffers from massive opportunity cost and for the most part being outdone by Mence, Aegislash is just meh overall for the same reasons as Rachi, and Clef is just a dogshit check to things it wants to check like Xerneas and Darkrai, its horrible stats just don't match up to the overwhelming power of Uber Pokemon imo. I've tried using this thing and its simply overwhelmed by Life Orb Sludge Bomb Rai with eventual, inevitable poison, and crits from Xerneas or SR damage. Sure it can stop Arc forms but even then it can be stalled out and you have Ho-oh or Snatch Blissey for that.
Shaymin-S doesn't really suffer from these glaring issues and is pretty much just better than these mons. You can't just nom it for a drop by stating things everyone knows like being frail and weak to rocks, priority beating it etc. These are the reasons it's not a higher rank in the first place. The mon has already been ranked taking into account these issues so saying them again shouldn't make a case for it to drop further. In general a Pokemon should drop due to metagame changes affecting its performance in a bad or good way, or being horribly wrongly ranked at first. Anyway to counter-argument Random Passerby:
"As stated, this thing can't switch in on anything, ever so you need to give it a free switch-in somehow."
While this is true, Shaymin's ground immunity can force mindgames with the omnipresent ground moves. Besides, Darkrai can't really switch into anything either but it's A+. Again though I feel this is bringing up things that were taken into account when it was originally ranked.
"Even when it comes in, you don't hit that hard even with a Life Orb as 120 SpA is really average for an Uber."
Tbh I think Shaymin's damage output is good enough. Some calcs for example;
252 SpA Life Orb Shaymin-S Seed Flare vs. 4 HP / 0 SpD Darkrai: 265-312 (93.9 - 110.6%) -- 62.5% chance to OHKO - gauranteed after a round of LO recoil or SR.
Outspeeding and OHKOing Darkrai is a huge benefit tbh, and the fact that it can OHKO shows that its damage output is actually decent, especially when you consider its chances to flinch (Air) or drop their SpDef to -2 (Seed).
252 SpA Life Orb Shaymin-S Seed Flare vs. 104 HP / 0 SpD Xerneas: 246-290 (58.7 - 69.2%) -- guaranteed 2HKO
This isn't really set up fodder at all, considering its at range of Ekiller unless significant defense investment, in which case you won't be running this much HP anyway, so Seed Flare is doing more damage. This is also in range of basically everything that picks off Xerneas (Ho-oh, P-Don, Scizor BP, Mega Luke etc etc).
The same applies for things like Ekiller and P-Don (lol Life Orb Earth Power). Mence is the only thing that can potentially set up freely as Shaymin is forced to Air Slash. TL;DR - 120 SpA may be weak, but Life Orb and a very high BP move in Seed Flare (120BP) with no drawbacks bar accuracy, and a huge benefit of 80% to drop Sp.Def negates this.
"Especially when you need to rely on Air Slash (as most Ubers resist Grass so you can't spam Seed Flare)."
Most of the things resisting can't switch into Shaymin anyway. Mence won't like switching into Seed Flare, dropping to -2 and then taking an Air Slash as it just dies.
252 SpA Life Orb Shaymin-S Seed Flare vs. 200 HP / 0 SpD Mega Salamence: 66-78 (17.3 - 20.4%) -- possible 5HKO
252 SpA Life Orb Shaymin-S Air Slash vs. -2 200 HP / 0 SpD Mega Salamence: 329-387 (86.3 - 101.5%) -- 12.5% chance to OHKO
Klefki fears Earth Power especially when at -2. The Latis, Dialga, Aegislash and the rest are hugely pressured just by being at -2 by switching into a Seed Flare. Ho-oh is for the most part reliable but Shaymin can and has run HP Rock to beat it, which OHKOs at -2.
Basically while Seed Flare is resisted by quite a lot of things, its80% 100% chance to put them at -2 simply negates the resist and leaves them very vulnerable to a coverage move anyway, or Air Slash flinches which ARE in your favour. Even when they have a Ho-oh for example, Seed Flaring it on switch in is better than Air Slashing it, to simply leave it vulnerable at -2 SpDef, so I'd say Seed Flare is actually really spammable.
Lastly Healing Wish is a stupidly good move.
Shaymin-S doesn't really suffer from these glaring issues and is pretty much just better than these mons. You can't just nom it for a drop by stating things everyone knows like being frail and weak to rocks, priority beating it etc. These are the reasons it's not a higher rank in the first place. The mon has already been ranked taking into account these issues so saying them again shouldn't make a case for it to drop further. In general a Pokemon should drop due to metagame changes affecting its performance in a bad or good way, or being horribly wrongly ranked at first. Anyway to counter-argument Random Passerby:
"As stated, this thing can't switch in on anything, ever so you need to give it a free switch-in somehow."
While this is true, Shaymin's ground immunity can force mindgames with the omnipresent ground moves. Besides, Darkrai can't really switch into anything either but it's A+. Again though I feel this is bringing up things that were taken into account when it was originally ranked.
"Even when it comes in, you don't hit that hard even with a Life Orb as 120 SpA is really average for an Uber."
Tbh I think Shaymin's damage output is good enough. Some calcs for example;
252 SpA Life Orb Shaymin-S Seed Flare vs. 4 HP / 0 SpD Darkrai: 265-312 (93.9 - 110.6%) -- 62.5% chance to OHKO - gauranteed after a round of LO recoil or SR.
Outspeeding and OHKOing Darkrai is a huge benefit tbh, and the fact that it can OHKO shows that its damage output is actually decent, especially when you consider its chances to flinch (Air) or drop their SpDef to -2 (Seed).
252 SpA Life Orb Shaymin-S Seed Flare vs. 104 HP / 0 SpD Xerneas: 246-290 (58.7 - 69.2%) -- guaranteed 2HKO
This isn't really set up fodder at all, considering its at range of Ekiller unless significant defense investment, in which case you won't be running this much HP anyway, so Seed Flare is doing more damage. This is also in range of basically everything that picks off Xerneas (Ho-oh, P-Don, Scizor BP, Mega Luke etc etc).
The same applies for things like Ekiller and P-Don (lol Life Orb Earth Power). Mence is the only thing that can potentially set up freely as Shaymin is forced to Air Slash. TL;DR - 120 SpA may be weak, but Life Orb and a very high BP move in Seed Flare (120BP) with no drawbacks bar accuracy, and a huge benefit of 80% to drop Sp.Def negates this.
"Especially when you need to rely on Air Slash (as most Ubers resist Grass so you can't spam Seed Flare)."
Most of the things resisting can't switch into Shaymin anyway. Mence won't like switching into Seed Flare, dropping to -2 and then taking an Air Slash as it just dies.
252 SpA Life Orb Shaymin-S Seed Flare vs. 200 HP / 0 SpD Mega Salamence: 66-78 (17.3 - 20.4%) -- possible 5HKO
252 SpA Life Orb Shaymin-S Air Slash vs. -2 200 HP / 0 SpD Mega Salamence: 329-387 (86.3 - 101.5%) -- 12.5% chance to OHKO
Klefki fears Earth Power especially when at -2. The Latis, Dialga, Aegislash and the rest are hugely pressured just by being at -2 by switching into a Seed Flare. Ho-oh is for the most part reliable but Shaymin can and has run HP Rock to beat it, which OHKOs at -2.
Basically while Seed Flare is resisted by quite a lot of things, its
Lastly Healing Wish is a stupidly good move.