Mogiee, the bottom line is that you miss the point. One or two airlines in the UK may have been doing CRM at the time but BMA were not (like the vast majority of companies) and therefore this crew had not had the benefit of such training. As a direct result of Kegworth the CAA later made it mandatory.
Further, when the right thrust lever was retarded (disconnecting the Auto/throttle in the process) all the symptoms all but disappeared. The left engine vibration became minimal because the A/T was not pushing fuel into it trying to speed up the flagging N1. Also the disconcerting yawing immediately ceased for the same reason. The left engine was then also retarded reducing the symptoms almost totally.
Yes the captain grossly added to his workload by handflying and by getting on the other box to find out what the company wanted him to do (where to divert because he feared the sack). The FO was talking to ATC. It took 15 mins from the start to crashing. No time at all to carry out the many duties to prepare for a rapid landing at an unprepared for airfield.
The FO added to the workload by trying to reprogramme the FMS. At no stage did they get a chance to review their decision which given the fact that the major symptoms had disappeared seemed correct.
As to the RAF being aware of CRM I find that a bit of a laugh given their brainwashing of all recruits not to question an order or authority. I have many personal experiences of RAF CRM.