I used thorn 100% of the time during IB once I was finished with the headshot bounty. It's a great gun but it's not unstoppable. I got beat one on one many times by people who understood tactics. Anyone who just ran at me in a straight line got mowed down. Destiny pvp is not "run and gun". Learn the maps, play tactically, and choose your battles. If you're consistently getting killed by one guy who's using a Thorn, you're consistently doing something wrong.