Maybe I am splitting hairs, but to me there is a kind of power leveling that is OK for new players. That is when you are in maps of your appropriate level, the threat is red, and you take an XP multiplying elixir. The kind of power leveling you describe is actually leeching, but the kind you can do with an elixir in your own levels is not leeching, and I think there's a big difference in that.