the thing about pvp/db can be changed to third place (if there was a battle for the third place) if so much players doesn't agree.
a lot of times winning a tournament means win 3 match, if u can't do it u aren't a good pvper lol, a lot of players are here from years, joining 2 weekly tournaments give u 24 tries/year (without counting the tournaments).
unfortunately this is the only way u can really know what a player can do; put something like "join 20 tournaments" can require a year to accomplish, i know that is harder than "draw a card"
about fun tournaments and "serious" tournaments: the mentality is almost the same, the luck factor is in any kind of tournament, i don't think is a problem if a player that won a sosa tournament wanna be a tutor.