I've noticed that every once in a while archer does not do an extra damage agains those lebeled with a death mark. I am quite sure that it was fighting someone at the point, and was not under a stun. So far only saw this at interserver battlefields, so can't provide fight logs.
Same thing has just happened again. A guy had 3 marks on him, but was not recieveing any extra damage from an archer. Interesintingly, it was working on mage guards in the same fight. So, is it a bug use or a special feature?