It does have a post/comment volume chart, but I don't know how reliable that data is. On July 1st, the API change affected both users (resulting in some leaving which should reduce those metrics) as well as mods (resulting in a reduced ability to deal with bots and trolls, which should increase those metrics).

Add in the complication that Reddit's admins now have a short vs long term conflict where the short term is helped by making it seem like the API changes haven't hurt anything and allowing bots to inflate numbers (or even run them themselves) while the long term would want to see bot activity stamped out so that more users aren't driven away by it.

I don't think we'll get a good idea of what's going on in the short term. In the long term, it might require tools to scrape the data without the API being available (which will definitely happen, you can't allow users to access something and prevent programs from accessing it because the browser itself is a program and HTML, which makes it possible for browsers to organize the information they display, also makes it easier to parse and separate data).