The bell curve is so last century
But then again, isn't the WoW set in an imaginary past/future?
I worked for an organisation that insisted on sticking with it, and yes, managers were given the task of allocating one low grade (2) and one high grade (4) while everyone else sat on the middle (3). The recognised procedure would them be for the token 2 to complain to Personnel/Union that they were being victimised (assuming they weren't dead wood, and deserved it), whereupon the 2 would be bumped up to a 3.
This worked well, satisfied the box-tickers, appeased both employee and manager and rendered the whole appraisal process pointless, as indeed it is if you insist on sticking to the bell curve.
No amount of logic seems to work with the advocates of this archaic process. All it does is waste everyone's time and company money, and generally hacks off the workforce. Again, sooooo last century.
Appraisals should be based on individual merit, not relative to others. If there is any scoring, it should be based on objectives agreed between employee and manager at the beginning of each period. If this then falls into a bell curve for a set group of workers, management can smile knowingly, and this is fine, but the tail should not wag the dog.