Ok that I disagree with. Politoed should definitely still stay S rank. Not only is manual Rain only last 5 turns as opposed to the whole battle (8 if you have Damp Rock which means you have to forfeit another item) it doesn't get set up as easily as simply switching in a Drizzle user. When you factor in times you might need to attack or support moves you're using within those turns, you'll find that those turns can go faster than one might think. Also, I think you're over exaggerating Politoed's flaws. It definitely does not simply do nothing apart from Rain. Drizzle alone is enough for S Rank in my mind, seeing how powerful Rain teams are and how many advantages Rain support can give a team, but it has a nice support movepool with things such as Encore, Helping Hand and Icy Wind. If that wasn't enough, it can still retain good offensive presence with either a Choice Specs set or an offensive Water Gem set. I don't see why a lack of spread moves is such a big deal when it's not hard to build around Surf, Hydro Pump in the rain hits like a truck on an offensive set, and Scald is Scald (aka being a pain to switch into because of the burn chance). While its stats aren't anything to brag about, 95/75/100 defenses aren't shabby and 90 Special Attack goes a lot farther when your STAB is essentially boosted a second time because of the rain you bring. Water is also a good typing, offensively and defensively. Furthermore, Politoed is able to threaten 3/4 of the other weather summoners (can threaten Abomasnow too if you chose to run Focus Blast but that's generally a very risky option) so it will be giving you an edge in the weather war when you're throwing around Rain boosted attacks and your opponent has to respond somehow.
Yeah, I suppose those are pretty good points, I just feel Politoed is fairly flawed and a bit much for S Rank. Rain is great, Politoed is... not as great, probably decent at best. My view is that it does not have S Rank's definition of "few to no flaws". Politoed has a lot of flaws. But in the category of "nothing other than Drizzle", I stated than pretty poorly. I was trying to aim at the fact that it cannot really perform any other roles. It relies on its weather role a lot, unlike Tyranitar, for example, it is going to be very lacking offensively outside of Rain. I just simply don't view it as being on the same level of those other three S Rank pokemon, each of them is stellar, hard to deal with, and can be chosen on a team for a variety of reasons. I also disagree with Water being a good offensive typing, as what makes Politoed's STAB attacks good is really the Rain boost, not Water's coverage. Additionally, from my experience, Politoed can only threaten Ninetales if Rain is up and not Sun, as since most Sun teams also have manual set-up methods, this is going to be pretty hard. Drizzle is obviously the best way to (and the only way you should) set Rain, and I was wrong to view Rain Dance as a viable alternative option. The question in my head is "Is anyone really going to pick Politoed for a reason outside of setting Rain?". From my experience, you aren't going to think "hrm.... I need a good Fire resist (or Icy Wind spammer), how about Politoed?" You are almost always (if not always) going to choose Politoed with the sole intention of setting Rain. That is really what I was aiming at by roles it fulfills. In terms of other things, there is usually going to be something better. In Tyranitar's case, you will often choose it without the intention of Sand. You might choose it because you need something to hit Cresselia, or you need something that can tank attacks, or maybe something to help defeat Trick Room setters in general. I might just be overdoing things by looking at them without weather (or comparing them in general), by from that viewpoint, Tyranitar obviously has something more, and this makes me think Politoed may be more A Rank than S Rank. Don't get me wrong, Politoed is important, since it is the only holder of Drizzle, but I really feel outside of Drizzle, it lacks any other prized roles, and this better fits A Rank's definition:
S Rank: Reserved for the top threats in the Doubles metagame. The pokemon in this tier are able to perform multiple roles to tremendous effect, whilst having few to no flaws. Support Pokemon in this tier can easily create free turns for their teammates without creating clear openings for the opponent. Any flaws that these Pokemon have can be taken care of with little to no team support.
A Rank: Reserved for Pokemon that function very well within the current Doubles metagame. The pokemon in this tier are either able to perform multiple roles to great effect, or execute one extremely well. Support pokemon in this tier can create free turns, but not as easily as those in the S Rank.The flaws that the pokemon in this tier may have are usually mitigated by their positive traits, or with minimal team support.
The "execute on extremely well" part is where I'm coming from. Politoed executes one role extremely well, but I'm not so sure about "multiple roles". It might have them, but it definitely does not perform them to tremendous effect. This is why I think our favorite frog should be A Rank.