A lot of the swarmers i've seen have done pretty well IMO (Tyson, Dempsey etc.) Who specifically are you talking about?
Of course lots of swarmers have 'done well', or they wouldn't exist. :huh Tyson is not, nor never was, a swarmer :nono - he was a boxer/puncher who happened to be under average height for a heavyweight; a stocky build does not a swarmer make. A swarmer is in part characterized by the old cliche 'take one to give one' - a defensive wizard like young Mike definitely doesn't fit this bill. The archetypal swarmer is, of course, Joe Frazier. To even be competitive with Ali (a pure boxer and supposedly the perfect foil for the swarmers skills) he took a horrible amount of punishment. A great contemporary example would be Ricky Hatton - look at the damage he accumulates in even winning efforts, that is not the face you would expect from a guy who's lost one fight. So, yes, lots of swarmers do well and are even greats, but its the LAST style I would want to have as a fighter- simply becasue it entails taking the most punishment.
Never really thought of it that way, frazier and hatton do take a **** ton of punishment. I still think of Tyson as a swarmer however, he fought in flurries and totally lacked a jab (which is pretty much required to be considered a "boxer"). IMO he is not a boxer/puncher, Joe louis comes to mind when i think boxer/puncher. Tyson is no Joe Louis .