As a pharmacy manager I lost one cashier/otc stocker to this round of layoffs. I can tell you that performance played no part in the decision of who to let go, and I had no input at all into the decision. The person they chose only makes sense if they were doing last hired first fired. It may be different for pharmacists, I don't know because we didn't lose any.
Was this the same at other Walmarts? The last hired, first fired system, that is. In an already bad situation, I actually believe this is the best way to go. Unless, of course, there are incompetent workers who need to go first.