Looks like an awesome trip! No darts, but a few thoughts.
For me, I would tweek a bit, as I am not as fond of the Black Hills area as I am w/ Glacier,Yellowstone and GTNP. So, I would add a few days to GT, and a few days to each side of Glacier. I am with 4runnerguy as far as liking the East side best, but both are wonderful.