In the grand scheme of things I don't believe docking tails is that bad. That being said I would not get your pups tail docked. I have a friend that breeds dobermans and she won't dock a tail of a pup that's over 3 days old.
There are literally hundreds of thousands of dogs out their with tails that do not have back problems. It is not likely your pup will develop back problems from having a tail.

Good luck with your new pup and have fun!