A simple observation of the number of dead mites resulting from treatment is flawed, as the number will be a function BOTH of the efficiency of the treatment used, AND the initial severity of infestation. So, one can obviously be confused with the other - and, in addition - the counting of dead mites says absolutely NOTHING about how many live mites remain - which is arguably what you really ought to be concerned with ...
A far better approach would be to assess the level of infestation BEFORE treatment, using either the sugar-roll or alcohol methods, THEN treat, and THEN re-assess a sample of remaining bees, using exactly the same assay method.
But realistically, is anyone really going to adopt such a procedure for EVERY hive, on EVERY occasion ? I doubt it.
LJ