I owned a HTC as first smartphone with slide keyboard. I rooted it in order to update it to current version of Windows Mobile. Sprint is infamous for their very late firmware updates ever one year after new release!
Have you tried download a firmware to smartphone WITHOUT battery inside? I pulled that trick on old blackberry phone after accident brick.
Are you using Odin? It's good hacking program for all android devices if you use correct rom. I used it to root my Samsung Galaxy S4 so I can 'freeze' the unwanted bloatware. Just search 'device model name' roms and you may find correct roms to fix the bricked devices. I was almost bricked my Samsung with wrong root files but Odin helped stop it until I found correct files.