Spells: Healing not landing at 0% (but still alive)

[Aesop]

Happened to me on my druid, cast chloroblast on myself when I was about to die -- got knocked over and according to the text it landed said I was blasted with chlorophyll or whatever healed for 428. My health did not change, and the next melee hit killed me despite the heal landing.

Tonight, was PLing a new recruit to red, he was at 0% health but alive (He didn't die, because the mob died to thorns on the hit that took him to 0%). I cast a chloroblast on him and it did nothing. I thought he died but he was still scooting across the ground at 0% so I cast another chloroblast and the second one landed healing him to full.

Anyone noticed anything like this?