I think I decided against an earlier response, but now that the great *lelle* has responded, I have more confidence to say what I was going to say.
I still use a Yamaha P80 as my main stage piano: single note trills? It's been as fast as I can manage. And I do use a lot of single note trills not just in rep but in improvising: it's fun.
The Rhodes piano? Yeah, it can be a bit sluggish to come back, the hammers. That's a great example of conception outstripping the ability of the machine.
But IMHO you really would have to be going Mach 1x10^6 to outpace even the twenty+ year old Yamaha graded hammer action.
I'd guess technique problems before blaming the equipment.
/* edit: So, what exactly is the problem? FWIW: I'm not a speed demon, although it meets my needs, but this comes up a lot in my own playing. I more or less put the forearm parallel to the keyboard, and just drill 3-2 or 3-2-1. Maybe 4-3. It depends on exactly the context.
I find the Yamaha action adequate.
BUT, no, it's not the same as a real action. I've just got used to it, is all. */