Are we suppose to lose Soul Vitality if we're killed by a player (100% -> dead) while in a PvE fight?

The Guardian group that I was in got rolled by a Defiant group and I ended up with a Soul Vitality of 20% (down from 80%) even though no mob ever touched me.

While the cost for Soul Heal is chump change it does seem odd that a non-hardcore PVP game (Darkfall or EVE; full loot) would penalize World PVP in such a way.

...or is this a bug?