I've yet to test with another hunter to see if there are any negative affects. Last night, another hunter in a LFR sigil run asked me if Hunter's Mark was bugged because his kept dropping off. After he mentioned it, I also noticed mine was dropping off. After a couple minutes, I came to the conclusion that it must be each hunter overwriting the others Hunter's Mark because of the glyph. Prior to 5.1, this would not occur. Is anyone else experiencing this and have any data to confirm that there is no negative affect? I doubt there is since a mark will always be put on the target, but would appreciate some feedback.