Thorn is not "bullshit." It's actually quite hard to use compared to TLW or even a good legendary pulse rifle like 123 Syzygy. It doesn't fire that fast, and you have to get headshots.
I just got Thorn, and it's my baby. I've been maining it for the Queen's bounties and even messed up orb generation during Crota because my DoT killed one of the knights (whoops). But right now, I'm doing way worse with it in Crucible than Vex, TLW, or Red Death.
Vex and TLW are basically newb tubes. You can spray and pray and still rack of kills if your aim is decent at all. Pulse rifles also don't require close to the level of precision it takes to pull off 2 headshots back-to-back with Thorn.
Here's the real truth about Thorn: it's OP in the hands of a great player. Well, so are most other guns. Watch Gaz run around the Crucible doing the Thorn bounty for the 4th time with Word of Crota racking up 10-kill streaks, and you'll see what I mean.