Well I've seen Mikhail and Vlad regularly dispose of small challenges at seminars and it's been recorded. Small because once their challengers felt what they had, they were reluctant to continue testing.
Martin Wheeler came from an extensive Kenpo background and was a certified bad ass before he met Vlad. He made regular trips to Toronto from LA and eventually abandoned the Kenpo throne altogether. Kevin Secours is another big name MMA specialist and he too has placed his hat on Systema's rack. These guys are dedicated martial artists and don't easily suffer fools.
I know it's hard not to label Systema's effectiveness based on this sad example but it would be unfair to do so. Frank Arias is hardly the standard by which Systema is measured. He openly admits he's still learning and I applaud him for testing himself.