Balancing is is a good idea if you are concerned or have vibration in the shaft . I worked a year or so in a machine shop building and balancing driveshafts, the first thing you have to do is remove the u-joints to mount the shaft to the lathe, if the yokes are bent you would only be able to try and compensate for it in the tube part, a good shop would be able to identify this and would probably recommend replacing the welded in yoke.