This is all a bit bogus really.
It's more likely Google made some changes in that Panda update that effected the site. I seriously doubt what you did was what made it recover. 15% drop is nothing, if it dropped 50% and you changed a few things and it recovered I may believe it. My site was hit with Panda at in September too and lost 90% of it's traffic, still no recovery and I did a lot of the things you said.
It's more likely Google made some changes in that Panda update that effected the site. I seriously doubt what you did was what made it recover. 15% drop is nothing, if it dropped 50% and you changed a few things and it recovered I may believe it. My site was hit with Panda at in September too and lost 90% of it's traffic, still no recovery and I did a lot of the things you said.