I just soloed this for the second time and the whisperer triggers far too often with the flashing light and attacks. With a group of four this never happens this much. Not even near this much. However the triggers are set, it seems like there is something wrong with a boss that does it's main boss move at a near constant rate. I don't know if this is a result of how the boss is designed or a bug, but again, it triggers far more than it does with a four man group.