A perfect example of how exotics should be is borderlands. Exotics should be crazy unique guns that are situationally great (fighting certain enemies, only good for specific builds, ect...), but not necessarily better than they're legendary counter parts. Unfortunately, and I really hate to say this, but the problem is pvp. You can't make really crazy fun stuff without people finding a way to abuse it in pvp. You even take something simple (putting a DoT on a handcannon) and it can get massively out of control. While I would love some new crazy exotics, I love destiny for it's continuous pve to pvp experience. It's one of bungie's main philosophies and it's unlikely to change. Hopefully the dev's can find new inventive ways to create interesting weapons while keeping balance relatively in place.