I think dribbler is not so important, I just trained a player with it to do further testing. But at the end no one exactly knows what advantages a special ability gives you in the game. But why would there be SA's when they were useless? I don't believe that, so dribbler and other SA's must do something for the calculations of the game.

I tend to play 4-5-1 V and have one of the wingers as corner specialist, one as freekick specialist, one defensive wall and 1 aerial defender in the defense. I don't like all the other SA's that much that I would train them additionally.