I actually took that completely the oppisite. It was STING AND ROGUE who had Friendship Power. Natsu had strait up full on super beat stick powers, and this world has shown, with the ressurection of Acnologia, that friendship power no longer solves all problems. Being overpowered does.
Either that, or the relathionship between Sting and Lecthor ISN'T FRIENDSHIP, when it clearly is.