All right so I haven't been playing since December, and Showdown seems to have changed a lot. I was wondering if someone could provide a guide or even explain.
I guess I'll answer this.
This is Smogons 'Format Dex'. Here you can look at every single tier that Smogon hosts. However, more info is found on more common tiers. For example, OU has more information than Smogon Triples. You can also looks the Pokemon in said tier. Sorry if this isn't what you wanted, but this is all I could find to help you answer your question.
Hope I helped!