From my experience the original rear shocks would have to be pretty well ****** to cause many problems. Unless they are leaking oil, or are sticking, the problem may be elsewhere.
I have a fairly new pair of Hagons, which you are welcome to try out / test, if you want ... just leave the CBF and keys as security

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As for the rear appearing too low - I've also noticed that one of my XBR's. A check of the forks revealed that the spacers are a few millimetres longer than the old XBR. The old bike handles much better

More investigation is required, when time permits.
Good luck