I'm not sure your interpretation of dribble speed is correct, over on the PES Stats Database it's described as "How quickly a player can move with the ball at his feet". There's a number of threads, here's one...
http://z4.invisionfree.com/PES_Player_Database/index.php?showtopic=1829
However the dribble speed stat on it's own doesn't determine how fast a player can move/run with the ball, but it works inconjuction with top speed.
The Dribble speed stat value is like a percentage of the top speed stat, therefore a player with a high top speed of 95 and a dribble speed of 80means the player can run with the ball at 80% of the top speed stat.
Still with me......
This could be worked out as a value, 80% (dribble speed) of 95 Top speed is 76.
e.g
Player A has a Top speed of 95 and Dribble speed of 80 = 76
Player B has a top speed of 90 and a Dribble speed of 90 = 81
Player B will be faster running with the ball than Player A.
Speed of turning with the ball and how many touches a player takes is mainly down to dribble accuracy as well as agility and technique.
I am with you and understand what your saying, but I know that dropping the dribble speed of players made them turn slower, but didnt seem to effect their speed when running straight.
Did you try the option file yet?