The Thorn is fine. If I ever get shot by one, I immediately rush for cover and put distance between us, then pull out my MIDA or a sniper and kill them. It's only ever in team fights where I'll die to a Thorn, and it's almost never the DoT. The people crying for Thorn nerfs are the same people that caused the SUROS Regime to disappear from the game: whiners.