Don't really agree with mixed sweepers being useless, it depends on the team and where you are at in the game actually. As my title post said, it is more than just what you use, it is how you use it.
Mixed sweepers alone aren't enough (not sense they banned HP Zapdos, anyway) that much is common sense, however if you have a team weakened to the point that one mixed sweeper can come in and do the dirty work, it generally helps. Granted most of the most dominant Pokemon this generation have no need to be mixed (Snorlax, Marowak) but to call it a "misconception" that mixed sweepers can break stall teams is foolish.
Mixed sweepers alone aren't enough (not sense they banned HP Zapdos, anyway) that much is common sense, however if you have a team weakened to the point that one mixed sweeper can come in and do the dirty work, it generally helps. Granted most of the most dominant Pokemon this generation have no need to be mixed (Snorlax, Marowak) but to call it a "misconception" that mixed sweepers can break stall teams is foolish.