Total dmg done per match doesn't mean very much, and nerfing a class because they spread their dot's doesn't make sense, teams shouldn't huddle so close together if they are worried about summoner spreading dots on them.

Nerfing for the sake of lowering the total dmg done statistic is incredibly short sighted, it is completely normal in every game I've ever played, for dot classes to be very high on the dmg done list because of how the dynamics of dot's and spreading works.