It is good practice to keep a consolidated library across versions for help documentation. You got it right with 10.1 -> 10.2. While ESRI documentation is amazing and well organized, it is not well served online. Please keep one URL scheme, OR make it easy for a user to access other versions of help documents.
What your peers are doing:
Related request: https://c.na9.visual.force.com/apex/ideaView?id=087E0000000fxT4IAI