I agree, Tom. Shearer ought to be classed as common in future.
It seems that the word shearer is used much more frequently in New Zealand and Australia than elsewhere. The attached chart is derived from the Corpus of Web-Based Global English, and aims to count only common noun usage, that it, excluding the surname Shearer. But this heavy usage down under just reflects the central role - iconic, even - of the wool industry in our history. But people can know what a shearer is even if they seldom come across the word. And as MK and RM indicate, that is no doubt the case.