I was always curious what this was. I've only ever seen it happen on Cerberus, though - my DoTs show on every other boss in WoD (though I don't put them on Cloud often because I don't want to push DPS - I'm a SCH - as I know how nasty it is to have worms up when the box-cloud phase starts)
It probably happens on Hunts, too, I just don't pay attention...there's only enough people there for that to happen on S ranks and I'm too busy healing people in that case.