It doesn't ALWAYS break follow, just if the "track target while cast bar goes for one second" process takes you off of perfectly lined up with your follow target. Most of the time, this is the case, but I've actually lost 1-2 hunters and had 1-2 stay on me after a long boss fight where everyone SS multiple times.

I am really worried about PvP and people infiltrating the ranks, but I guess that's what traps are for...