you know you can still do your normal snapping when you are adjusting the pivot...so should be easy enuf to get it where you want it. if you just do this around wrld origin, it'll be even easier, just snap it to the grid origin.
after doing this, and you pop a rotation into the correct box in dup options, and a numebr of copies...all should be fine. nothing special is going on. i'd check to make sure that you are indeed moving the pivot of the the thing you are duplicating, and it is that transform you have selected when you do your duplicaitons.
keep trying.. or maybe orientation of your local axis is a bit funny? ...when you;ve taken the pivot to your radial centre, there is an axis that clearly sticks out perpendicular to the radial plane? the axis you are using to duplicate around.
experiement w a box, just to convince yourself it does what you expect.
