Well actually, Thunder Wave Mew is very good to mitigate other Mew's chances (try to force an even trade with them booming). Reflect + Thunder Wave, Softboiled + Transform is what I'd call the standard Mew set. Transform will probably have to be banned because of infinite PP dittos, but something like Thunder Wave, Swords Dance, Softboiled, Earthquake is not a bad compromise when this tier isn't full of birds.
Not an arguments against Tauros though - it wouldn't want to screw up its chances by switching into a body slam and proceeding to get FPed. It's important to recognise when Tauros is played badly and that this is a new tier environment for skill. I think Tauros is pretty good at taking out the minor pieces which support the ubers (even it's hard to switch in), with it's high speed and CH ratio (yes, it's exhilarating though because it could not end up doing enough, e.g. by getting crit back). I feel Snorlax is correctly ranked a little higher due to getting a bit more chance, thanks to chansey's weakness to boom (light screen chansey), to paraslam and get sufficient opportunities to boom. Snorlax's weaknesses are that it can't really pull of resting well consistently, and as has been said, it doesn't get much chance to boom on the defensive, and can therefore be predictable.
About Mewtwo Psychic on Slowbro, I like the crit being a 3HKO, because you can force it to rest quickly, not suffering much PP loss, allowing you to go to your own Slowbro or whatever.
Regarding the viability rankings, I'd like to know what cores are viable versus the classic Chansey and Slowbro combo, because I'm guessing Starmie is a question mark of even being viable (is a fast poor man's slowbro useful?) if everything ranked lower is compared to it. Ortheore is correct in that the classic core restricts teamslots, but the question is whether or not you keep the same high chances by abandoning it partially. I have no doubt you can beat lots of players without it, but I'm asking for: for and against using it in various scenarios.