Yes, videos do prove fair game-play, unless of course they are edited from a multi-PoV and hide 'certain things.'
However, what would happen if for example a guild kills a boss, gets realm first, but doesn't have a video to show? As we all know, bugs could exist when those bosses are released at first and their could be ways to avoid certain mechanics and such. That's why I'm asking to see if anything can be done to combat kills without proof or evidence of fair game-play :)
It definitely would not be fair if, for example, X raid killed a boss in a non-legit way and did not provide anything to support their claim of realm first(Pics don't really count). That would be quite sad for all the other guilds that were trying to do it appropriately, right?