For purposes of feedback:
1. I have installed the latest version of CrossOver, with Tralfazz's recommended settings.
2. Ingame freezes on my main character continue to manifest themselves in an irrational way; he sailed through a tier 3 version of the long and very crowded 12-man skirmish Doom of Charas Gelebren perfectly, and froze three times within five minutes in the daily Forges instance - freezes of 1min & 30 seconds and 2 minutes long.
3. On at least two occasions, after a sudden slowdown followed by a freeze, I found that the Texture cache had reset itself from 1.0 to 0.3.
4. Other characters are not affected.
5. Rather than curing itself for good, the phenomenon of restarts on the main hard disk running Sierra resulting in Bluetooth switching itself off is becoming the rule rather than the exception. An irritant rather than a major issue, as I have to then plug in a wired kb, access Terminal, input [sudo pkill bluetoothd] and then restart again...
6. As ever, unlikely to be either a hardware or a server error, since everything else works well.

Go figure!