The network monitoring system collects transmission and/or receive power level information from a plurality of customer premise devices connected to the same distribution node for each of a plurality of network distribution nodes. For an individual network distribution node, the network monitoring system calculates a set of fluctuation parameters including a group power level deviation metric, e.g., a modified standard deviation ratio. The network monitoring system evaluates the generated fluctuation parameters and responds, e.g., outputting a fluctuations report, modifying a data collection profile being used by a set of customer premise devices corresponding to a distribution node, commanding diagnostics to be performed on a portion of the network and/or directing a service technician. The network monitoring system compares generated fluctuation parameters corresponding to different distribution nodes, and uses the results of the comparison to assign priority with regard to the assignment of limited available troubleshooting and repair resources.