A lot of things to discuss, wonderful
First of all i agree and i'll glad to see a Garchomp rise. Despite the x4 weakness and how common lando and gliscor are atm, garchomp can do his job extremely well. Fat "rocky" Chomp is really good now, it can set rocks whenever it needs to and can let suicide the most threatening phisical attacker of the meta. With Mmetagross in the meta, garchomp is a very valuable mon to use as a reliable check to it (meteor mash is 3hko suicide). Garchomp still do not die to Mlopunny ice punch, it punishes fake out and kill with EQ. It can even take a Play rough + aqua jet from Azumarill and it is a good answer to the band set too if not switch in a play rough. The set let it do what it needs to, rocks, standard EQ, fire blast for opposing ferrothorn and scizor and dragon tail for stopping enemy setup and it is actully a pretty good answer to Smeargle's GeoPass. I think a rise can be a good thing for it.
Speaking about Chansey I can't actually see a rise. It's fine where it is. It is very dependant on knock off, it is taunt and setup bait of a plethora of things and can only be played on Stall, a playstyle with the ability to balance the negative effects of its passiveness. I can, instead, see a rise of Skarmory do to the access of ita suicide lead set. Being able to fit both on stall and offense is a good point for it and maybe this could be a good reason for a rise.
I don't agree on a Ttar rise too. Yes, it's the best trapper in the meta and it's very common right now but looking at the A+ rank, i don't see it on the same level of things like Maltaria, Mlopunny or Gengar. Despite its good bulk it's easy to take down, its speed is good but not so good, not being able to revenge a plethora of thing. Yes, it's a good stop to talonflame (fuck will o wisp :-( ), it's the best pursuit trapper and it's good thanks to how well it pairs to things like Lando-i and for setting up sand for Excadrill. This being said, i don't think this benefits cover ita flaws and I think A is enough for it.
Just a thing on Mlopunny. Yes, it's easily revenged by Talonflame, but please, Landog can't come in, fire off an EQ and ger a kill, it can't neither after 3 SR damages on lopunny and it (ofc doesn't want to take a ton of damage), can almost kill back with Ice punch.
Have a good day people!