So lately you may have noticed that many of the Hotfixes being released for Vault 2011 and 2012 are now cumulative. So a Multi Issue Hotfix, which should contain most (if not all) of the hotfixes that preced it. There will still be Hotfixes released to address hot issues, but these should be consumed with the next Multi Issue Hotfix.
There may also be a situation where a specific Hotfix is released immediately prior to a Multi Issue Hotfix, but is not consumed within it. In that case, Autodesk just could not get it published in time, but did not want to delay a big patch that could help most users. You should look at the readme of the Multi issue Hotfix to see if any issues you are experiencing are listed. If it is not listed, it should be consumed in the next Multi Issue Hotfix.
So as a rule, always install the latest Multi Issue Hotfix, and any other relevant Hotfixes between that and the preceding Multi Issue Hotfix.