I think the system is very inconsistent.
You can farm the 4 hours the even lasts and still get 1 ball, while a person who has done half the farming you did, gets 3.
Obviously speaking of +30 levels here, because I've seen that the higher your level is, the harder it is to get a ball.
And to be honest Dragon Balls (tier 2) aren't the most special objects in the game, since most of the people are just going to use them to get their transformation (super saiyan, great namek, kid buu...) or maybe equipment, and then move on to something else, like for example getting to a higher level, doing budokai tournaments or so.
I've seen some people that created another character to get the balls from another launcher with the character they want the balls for, and I think that if you have to do this, the game loses his "fun".
The droprate is crazy, half the times the ball icon appears, nothing will come out of it.
I would elevate the drop probability at least a 10/15% since the point of a game is being fun, and not frustrating, which happens when you play and get nothing, seeing that effort you made into actually killing mobs is POINTLESS in many cases.
Again, very good job with the game guys, but this... this is just, not the best.
EDIT: This is NOT a hating post, this is just a pacific, friendly suggestion.