Thanks for the links, but unfortunately they weren't very helpful. I'd already run through most of the 'fixes' in the linked forum post to no avail. I've tried drawing in both 8 bit and 16 bit files, changed preferences, calibrated the monitor, made sure drivers were updated, etc.
The only new suggestion I found was changing the cache level to 1. (Mine as at 4) This did have some improvement in brushstrokes in 8 bit files, but didn't help the 16 bit files at all.