Removing one strap (patta) of leaf spring is not recommended. Your vehicle will loose the ground clearance and when couple of people on board you will have even worst feeling while driving specially crossing the speed bumps.
To me it seems one of rear shock absorber of your vehicle is gone. Check closely if you see some sort of oil or dark black spots on anywhere on the shock?
Plus there is a desi method also.
Park your vehicle on flat surface. Stand in front of the rear wheel, put your hands on its roof/rooflines and try to push it down with jerks and simultaneously observe the behavior of the shocks too. If you feel them bumpy, like they immediately (in split second) move up, it means the shock absorber is ok. And if you feel it very soft and it comes up with soft feeling, it means this shock is not working as it should.
BTW, even if its one rear shock who has gone bad, you have to change/replace both of them together.
