Agreed. Chansey has been ignored for serveral reasons this round, and I am sure its usage is down for mainly these reasons:
1). The banning of Kyugem
Kyugem had very few things that could take its hits, mainly due to the lack of useable steels in UU (Cobalion is probably the best, and maybe Steelix/Durant to a lesser extent). Chansey was one of the few pokes who could wall nonphysical Kyugems, and even with 101 subs, this poke really had no way of hurting Chansey.
2). The increase of use of Staraptor
While I haven't laddered as much, during the beginning of round 2, staraptors were everywhere. Banded raptors might be able to 2hko, but it required double edge or BB to do it, since Close combat was, I believe, a 3HKO (sad, isn't it)? Chansey might be able to check staraptor, but it definitely can't switch into it.
3). Being adapted to.
Since Chansey was not banned last round, this round, teams have been built to handle the blob better in multiple ways: Using mostly physical attackers, and maybe 1 or 2 special attackers, or the much more successful "Tickle Trapping" (which involves Wobbafet + dugtrio/pursuit user), the meta shifted around this defensive atrocity.
I am sure there are other factor I may not be accounting for, but having only one weakness, and getting hit oh its weak side with a SE hit and not dying just seems stupid. And that is ignoring the fact that anything special not named Raikou (and even then, Raikou can still lose) is never getting past chansey.