Unless you actually prune off the bud union there is no such thing as
"too much".

Gary J. Toth wrote:
Being new to roses, I've gone and over-pruned my Don Juan. I mean I
really butchered it! It's alive but God knows how. I've got it in
the planted to cover the union bud in some really good potting soil
and added about a 1/2 cup of epson salts. Is there any hope? There
is one good cane and one that looks like it MIGHT survive.

I know... SMACK SMACK SMACK ... baaaaaaaaaaaad boy!