New to iRules: Need persistance based on virutal directory

Actually, you are very close. Since you already have persistence enabled on the virtual, all you need to do in the rule is disable persistence for the urls you don't want it on. Try changing your rule like this:

 
 rule sautooffice_uri {  
    when HTTP_REQUEST {  
       if { not ( [HTTP::uri] starts_with "/sautooffice" ) } {  
          persist none  
       }  
    } 
 }