When enabling your toon's floating health bar a companion's bar can sometimes overlap giving you false information.
The "Player bar" should always be the top-most bar, followed by party etc..
Live seems to be okay but since there are soo many variables I can't be sure.
EDIT while on this topic : As you lose the visual color cue(green/red) when the bar is low or depleted it may be valuable to add some other means of identifying downed friend/foe - e.g. color of level in the circle left of the bar - (<red>70</red>)| | | | |.