I'm not EPAK, but as part of the Kenpo family I have heard and read both sides of the argument countless times. I have no kenpo in my area with an instructor I'd be motivated to train under, so I'm a video student with the IKCA, and I supplement with as much private instruction from GM Vic Le Roux as often as possible. I spent a year working on just the orange belt material before I tested, with lots of feedback. I am not familiar with any other video testing program, but the IKCA feedback program I have found to be most beneficial. As expected virtually nobody comes through the testing program without mistakes necessitating correction, and if enough flaws are found people can (and do regularly) fail their tests.
We go back to the drawing board with the corrections from the test results, fix the errors, and resubmit. Rinse, repeat, and you'll get it right eventually. Some are quick learners, some take several tries. The feedback is the key. Otherwise there is no way of ensuring you're "doing it right." Can video teach you all the intricacies - no. But if you're in the boonies - or like myself, at a lack of quality instruction with reasonable travel times - a program like the IKCA that offers feedback for correction, is far better than grabbing a friend and trying to "blind lead blind" teach each other, or merely watching and imitating.
As previously stated, I have a preference for a live instructor - however, in the absence of someone that motivates you as well as teaches quality material...a quality video training program can be effective. Note: I said quality - meaning multiple points of view, continued development with corrective two-way communication, and accessibility for feedback.
My 1/50 of $1.