Almost all bees will test positive for DWV if the test is sensitive enough (we've tested thousands) ... so there seems little point in testing for this, the most important virus of honey bees. CBPV, the new kid on the block, can also be detected in totally asymptomatic colonies.
I think what matters is symptomatic disease caused by viruses - and the two important ones are relatively easy to diagnose.
If you're going to pay for testing make sure you ask about the sensitivity and specificity of the test. The 'cleanest' bees I have still have ~1,000 genomes per microgram total cell RNA of DWV. Highly diseased colonies have about 10,000,000,000 genomes per microgram. A worthwhile test needs that sort of dynamic range ... and must be able to detect all strains of what is a variable virus. If it doesn't, you're wasting your money ...
... and since the viruses will also probably be there in the absence of any symptoms and at levels that should be of no concern, you're probably wasting your money anyway.
If you've got mites, you've got viruses ... and you've got viruses even if you haven't got mites!