This happened to me five times in the past three days, once while soloing, four times while in team.

While in a seperate room from the fighting, I received a barrage of attacks from the mob that equaled to my full hitpoints. In all cases, the agro was held either by my pets or by my teammate in an entirely different area and there were no adds. Somehow I was able to crawl around with 0-10 hitpoints, but when targeted by a teammate, I had full hitpoints. I was also unable to use a treatment kit, my healing pet, or the 15 point healing nano. While in teams, I just zoned out to find myself with full hitpoints and everything was fine. When I was soloing, the mob killed my attack pet, and promptly killed me. It sucked.