There are a few holes in your nomination, for one, any swift seimmer is a potent sweeper under rain. But the problem with rain sweepers is how to get the rain up, and swamp suffers from that when more than other rain sweepers, the problem is getting the rain up, and if you use a setter thats not swampert pre-mega evolution, then you waste a lot of rain turns. If you run rain dance, you miss out on coverage such as rocks, rest, or even ice punch. So keep Pert-M in A
Mega Swampert is a savage and has almost no trouble setting rain for itself. Set up on MAero and you're in for 4 turns of fun with a crazy powerful Waterfall. In addition, Jolly Pert beats pretty much every scarfer in the tier under rain. This is only the Rain Dance set though. Other sets like Bulky Attacking Rock setter can be used to provide hazards while still hitting incredibly hard (think Nidoqueen). Even SpD Rest Talk has seen play on various stall teams as a reliable answer to pretty much every Chandelure and other special attackers. Pert is a crucial member on offense, a viable member on bulky offense and balance, and a solid choice for stall. It's a mon who can fit everywhere and be damn good in everything it does. A+ is certainly something to be considered.
I think Cress is fine where it is. It has cemented it's place in Stall nowadays with it's aftermentioned insane bulk, and while it's CM set may be outclassed (don't know, I've never tried it) It's defensive sets are really nice. It can take a hit from just about any pokemon and hit back with a thunder wave, toxic, or a weak psychic. I've even personally ran moonblast to take out hydra. And while it's movepool is pretty barren, it has what it needs. It has dual screens for helping set ups, toxic and thunder wave to stall and annoy, psychic
I've tried to use Shiftry several times and it's just so underwhelming. It's pretty weak, extremely frail, and its useful niche aside from defog is neutered by the things its supposed to check (sucker/knock off, scald burn). In addition, Defog on offensive teams is fairly counter intuitive. Offense doesn't give a shit if hazards are up most of the time; in fact, they'd rather have hazards on both sides than on neither side, eliminating Shiftry's niche. Other than that it's okay but the amount of stuff that comes in safely/threatens it out is too high for a B- rank mon. Drapion is also pretty underwhelming and could see a drop like people are saying. However, I haven't used it recently so I'm not sure.
I get what you mean. To be honest, it has done pretty well on the team I showcased on your thread, putting enough pressure on opposing water types and defogging away hazards when I most needed it, as Victini and Mence needed to be healthy or I would get destroyed by fighting types. This may just have been because Shiftry was like the perfect answer for the last slot on my team, it almost always did its job every battle, but I haven't tried in any other scenario. Nevertheless, looking at what is on C rank (Gourgeist, Spiritomb, Blastoise), I am definitely going for Shiftry on there rather than not been ranked at all, as it does have a good niche that may come in handy sometimes.
Going to try to build a cacturne squad, my only gripe is how slow the thing is. Base 55 speed is well, pitiful to tell you the truth.
I respect the innovation and don't want to seem rude but there's almost no viability in Trapinch. It has literally zero bulk and requires too much effort to fill an extremely niche, unimportant role. Also I'd suggest getting higher quality replays against better opponents to showcase the mon next time you nominate something.
