Either Vic's appearance was based on a real person, like the EMH series, or Mirror!Vic was an android. We never actually got a decent look at his wound after he was shot.
My theory has always been that Vic was actually the "puppy" computer virus from s01e16, growing up and trying to get more interaction with people. That's how he could transfer himself between holodecks and access station systems. In the mirror universe the virus infected an android body and not a holodeck program.