Wow, those must be *some* scratches. What kind of paint are you working?
PI-II (39002)/cutting/rotary at 3K (!) is one *very* aggressive approach. I've removed pretty serious marring from hard Audi clear with far less speed than that, but it did take multiple passes. Using my Makita and PI-III RC (a little milder than yours), I took out everything that could be removed (*safely*) from the S8, but I spent a very long time doing it (note that I was being really careful).
I hope you're not trying to remove scratches that're too deep to work safely, but it doesn't sound like it.
I think I'd a) slow the machine down so the RC doesn't break down too fast, b) work the area longer, but with multiple passes *not just one long session that'll heat up the paint too much*.
Perhaps you're just expecting the rotary to do its thing faster than is realistic. I spent *days* doing the S8. I know some people knock out a vehicle in no time, but I don't expect to be able to do that myself.