In this paper we verify the insufficiency of Stevens' power law to describe the relationship between QoS and QoE factors. User studies that target different types of application scenarios of 3D Tele-immersion (3DTI) are conducted and the results show no significant power trend in the relationship between packet loss and perceptual quality metrics. We further verify that activity characteristics, activity objectives, and users' roles in the 3DTI session also have profound effects on the service quality aside to the QoS level. Thus, simple one-factor psychophysical laws are inadequate of serving as a QoS-QoE mapping model.