Yesterday I removed the discs and, sure enough, the friction discs are severely worn. Here we can see by the shallow grooves that the disc is about half worn.....
......and here's the flip side of the same disc, which is completely smooth. Someone's been doing some hole-shots with this clutch.
The discs are not warped and there's no indications of excessive heat, so the steel discs could be reused if needed.
But I'm replacing the discs with a new Barnett clutch set — friction and steel discs (this photo shows the Barnett friction disc with the OEM steel plate).
Clutch swaps are straightforward mechanics and everything went together smoothly — and my clutch is back to normal.