I wouldn't say some. I'd say that the vast majority of people who compete in events like trials and iron banner use thorn almost exclusively. In regular PvP it's not as bad, but rarely have I come across a match where there isn't at least one person using it, be it on my team or the enemies. And if I remember correctly there was I time when there was widespread red death usage, it was directly after the pulserifle buff. But please explain how that would be worse than thorn, I know that kills restore your health but there are many other weapons that can counter it effectively where as with the thorn it really came down to a few select guns and the players own skill.