I have to agree there. If Natu is going to play hide and seek, then we remove it's wall. With the dual types of Flying, then our last option is spam Tackle/Scratch respectively. An all in on Hoppip should be too enough to render it's healing useless. After that, just use Aron as the tank and teach the bird how to handle a crash course in failure. If Aron uses harden anymore, then Natu will find it nigh impossible to defeat him.

Nincada plans on helping by Scratching Hoppip, and if he is still going by the time we get to Natu. Using the same tactic that Natu was using. Using Aron as a wall and Scratching when the opportunity rises.