You can keep it if you want. But I would recommend Naive or Hasty Nature so you can use the Leaf Storm+Leaf Blade combo. But Timid is good so I guess you should just keep it or if you really want an in game beast keep trying for Naive or Hasty.
Hope I helped!
I don't think so. Serperior gets some good physical moves as well. So a Hasty or Naïve nature would be better. but you could keep it if you want to run a special set.