Solved! Go to Solution.
Might you be using operating system authentication for tracking and even though you have 3 users with different versions in SDE, they are all logged into the same computer with the same credentials which is what Editor Tracking is using?
My organization tested Editor Tracking in Oracle 11g and it worked as expected. Maybe it is an issue with SQL Server 2012. I would log an incident with ESRI if no one using SQL Server 2012 responds to your post.
Unless the 2 other users changed the version in the mxd from joe's to their own, they will be making changes as joe. This is 1 reason why sharing an mxd that can edit SDE is dangerous as you are providing other user's to someone's SDE version.
But did you create your own version to edit the data and replace that version in the mxd and save the mxd after making the version change. Unless you actually change the version in the mxd to your own, it will always use joe's SDE credentials.