Full fix, with the possibility of a short-term private pack "band-aid" to allow larger server admins the chance to warn their users. However, it would be optimal for the full fix to come with a complete changelog as if changes were made between the same versions (DW 1.1.1 -> DW Full fix 1.1.1). That way, admins of small servers might be able to check placed entities & make manual changes without having to perform a full world restart.
Everyone makes mistakes, and it does suck. I know I may not speak for everyone, but I can't really hold it against anyone. Last time I checked, I don't recall having to pay for any pack included in FTB - and it's still being provided. Best that can be done is to fix the error and move forward.