Olaf is currently working on a new DiskDoctor to address this issue.
Um, well, this is still a work in progress and based upon a rewrite from scratch (there is no sense in rewriting or porting the original DiskDoctor). The goal is to make a command line tool which does three things: a) detect and report file system damage, b) recover data from a file system and c) repair any damage found.
The detection operation is a prerequisite to recovery and repair, and it will never modify the contents of the file system. You can save the information which the detection process gathered to a file and then use that file as the basis for recovery or repair later, or you can of course rerun the detection before recovery or repair are performed.
The recovery operation will likely work similar to how DiskSalv would do the job, with the difference that you would have a choice to copy only those files which are sound (like a "copy #? all clone" command), only those files which are not known to be sound (deleted, corrupted, etc.), or to perform a "deep salvage" operation which would copy everything that is even remotely recoverable, including data file fragments.
The repair operation would excise any damage found, returning the file system to operational state again. This is what the original DiskDoctor was intended to deliver, except that it rarely accomplished even that, and could be depended upon to leave the file system in a much more damaged state than it was before. You would use the repair operation only if you had previously recovered all the salvageable data.
The new DiskDoctor handles large volumes, on storage media larger than 4 Gigabytes. It supports all Amiga ROM file system flavours including dircache and long name mode, with block sizes up to 65536 bytes. Because large volumes need to be supported, covering hundred thousands of blocks, the new DiskDoctor is specially optimized to use as little memory as possible for its work. You may still need 10 Megabytes of RAM for very large drives, mind you.
This is a rather large project, I'm afraid and I cannot currently quote a release date.