You forgot "and pass massive wishes to the rest of its team and heal their status problems and set up stealth rock and spread status". If you're willing to switch mismagius, alakazam, or pg-z directly into chansey then you're either playing really shitty opponents or you have pretty massive balls, because all it takes it "chansey used thunder wave!" and you're essentially down one poke.
The only way to really beat chansey is if you're also running a stall/balanced team and have a pokemon that can set up on it (roserade, deo-d, etc). If you're running offense and you somehow manage to switch into chansey with something that can actually 2hko it, you still have to deal with the fact that it either just wished, took off 33% of your health with stoss, or healed all the statused members of its team. This wasn't as big of a problem in this last metagame because the most popular Pokemon that chansey gave a free turn to (staraptor, wobby and espeon) were so absurdly dangerous that they were able to overcome any set up that chansey itself managed to do. But since we felt the need to ban these offensive/support threats (and they did deserve to be banned), chansey has only gotten stronger, significantly so. And if we keep banning offensive/support threats while telling people "just run knock off :D" then I don't see how this metagame is going to be anything other than a stall circlejerk. Again.
I really wonder what would happen if we dropped Giratina into UU; would that even get banned? People would probably just say "meh the defensive set is vulnerable to all hazards and it has issues with u-turn and it can really just sit there and be fat so let's keep it around" and then maybe ban it because it has really strong draco meteors.
I think there needs to be a fundamental change in the way we think about defensive suspects, because Chansey is so perfectly described by the defensive characteristic that it blows my mind that it has not been banned yet. Chansey is as representative of what is imbalanced in a metagame with respect to defense as Staraptor was with respect to offense and Espeon was with respect to support. That fact that all of these pokemon could be beaten (skill swap works great against espeon!!) should have no bearing on the fact that beating them is disproportionally difficult and causes a drop in metagame diversity and, ultimately, fun. This is much more difficult to see with defensive suspects, simply because they can't just come in and start KOing things like staraptor could. Their impact is spread out throughout the course of a match, especially in the case of a defensive supporter like chansey. Maybe that's why people think it's not a problem. Or maybe people have just gotten used to looking at a special attacker and saying "meh this can't beat chansey let me not use it" or "meh this can't beat chansey, let me devote two more team slots to ensuring it can". I don't know, you guys tell me.