Haven't been checking the variable caves at all, so I'm not sure about them. In the past, the caves had a chance of being empty. But if it's empty all the time, I doubt it's supposed to be like that.
I haven't been farming at all lately (*gasp*) but other people must really be picking up the slack, because I'm still checking the spawns and they're mostly staying low - which is, of course, why I haven't been farming them.
I suppose the rates could have also been changed again, but it's hard. I'd have to check something no one ever hits, and I'm mostly lazy this ten days.