The libc issues you are referencing are caused by RALUS being compiled to work on RHEL 3, 4 and 5. We can't use the C libraries that ship with RHEL 5 because they aren't available on RHEL 3 or 4. You can use up2date to install the compatability libraries on RHEL 5 which RALUS depends on.
Without knowing exactly how you are performing your backups, I would guess from your message that you are backing up a Samba share. This may well be fine for you. Backups via Samba are actually supported - see the software compatability list. (
http://seer.entsupport.symantec.com/docs/295304.htm) When backing up via Samba, you lose most of the file metadata such as security, ACLs and extended attributes. You also risk changing non-English filenames due to Samba configuration settings that affect how these filenames are converted to Unicode. Finally, using RALUS gives you the option to compress and encrypt the backup over the wire. Backing up via Samba will transfer the data via SMB which is in the clear by default.
Incremental backups using modified time are supported via RALUS. Were you experiencing performance issues with them?
Finally, none of this is new to RALUS in 12. This functionality is all present in the 11d RALUS as well. As far as I know there is no article pertaining to RALUS changes specifically.