lol, i dont know if I would call it unduly complicated. it would take only a couple minutes to set up, literally. But, yes, there may be a feather option. I just havent used it.
The mask I created before was not a simple letterbox. I had to vary the amount of transparency in certain sections (thus, a simple feather tool in Vegas wouldn't have sufficed). I would be surprised though, if Vegas didnt have this ability built in, or a plugin available