I've never heard of this "different chipset" that you're talking about for the latest production run of the REV2?
The REV2, Prophet 08, and a few other DSI synths all use the DSI120/PA397 chip, which is a slightly modified version of the CEM3396 from Curtis ElectroMusic back in the eighties. Definitely not one of the best sounding Curtis chips out there IMHO. It is a DCO based design. The DSI chip was custom-made for Dave Smith in large quantities in the late 2000's, and my guess is the Prophet REV2 was a way to get rid of overstock of these chips.
As for your filter question, the Moog ladder filter is behaving this way by design, it's a hardware thing. But several other music chip companies have their own design which often boasts a constant amplitude no matter how much resistance there is, like some Curtis chips for example.
BTW, I don't really like the sound of my REV2. I much prefer the sound of my OB6. But that's a matter of personal preference.