It IS useful, sorry I maybe confussed you

Sorry!
Lock Pick I find useful!
But I do not max it out early in the game! To the time I go to the Battle Tower, I have go to all chests that are still closed and try them after invest an extra point in Lock Pick. I can't remeber if there is a chest in Brocken Valley or Sentinel Islands BEFORE I have my Battle Tower that need "Lock Pick 5/5"!(?) Try it and see.
So, do what you want: max it out early, so fast as you can or wait and make first other skills on a higher level.
It's all up to you KnuckleHead!
