Myself also. I personally wonder whether I am following an appropriate workflow in these cases; my current approach is very basic:
1) I try to identify the 'corrupt' RAR either visually when it's filesize stands out as being different or using the HashCheck
shell extension in conjuction with an included SFV file.
2) I return to the indexing site and create a new NZB containing that RAR and the 'biggest' PAR2 file.
3a) If on second download the RAR is good I have to manually move the RAR into the existing rar-set directory, replacing the corrupt one and run an unrar program myself.
3b) If step 2 again yielded a corrupted RAR I go off to see if it was reposted to Usenet.
Am I correctly using the PAR2 scheme in step 2? In the case above I will have one RAR and one PAR2 file in C:\downloads\complete\release rarfix\ and everything else (for example, nine RARs, one NFO, one SFV and one SRR) in C:\downloads\complete\release\. Are PAR2 files there to allow repair of individual RARs on their own or am I supposed to make sure all files reside in a common directory first?