Funny thing about the 6.09b vs. 5.84c issue
Is that in tournaments 5.84c is used because it's the last version to be used before the transfer to the 6th series. Unless Team DAS stopped Dota at 6.09b then you still see people playing 5.84c.
I remember that there was a tournament for 6.0x something that was announced for weeks before, but as time goes nearer to the tourney date, people were already playing the updated versions. In the end, they decided to say and screw it and decided upon 5.84c. Which alot of people joined.