There appears to be some skill (possibly Suppression) that can cause other players' auto-target to switch away from an enemy. This happened today while we were in Uncharted Ruins, fighting a Vular Tankoid, causing me to fire at the other Vular Tankoid next to it (waking it up, and causing me to be under attack from both!) before I realized what was happening. We recovered, but this is very irritating.