You have assassins that do nothing more than sit in galadon marking and stalking players who are returning to galadon to log out, maybe for a short period to do something unrelated, and then come back in. Half of them probably have no idea the assassin is even there or that they are marked. They should not be punished for having to take a brief break.

Until a pattern is seen, I think people should be left alone. You have a problem with mark and its limitations, don't play an assassin. If you suspect some ranger is abusing logging out, pray about it. The mechanics probably work well enough as is.