It's fine, I can out gun a Thorn with my Last Word. Is it annoying being killed by the DoT of it? Yes. But you can also get people with DoT from grenades and supers so it's not that big of a deal. Just because so many people use it doesn't mean it should be nerfed. Make other weapons better because if you nerfed Thorn suddenly Last Word becomes godmode and has to be nerfed too.