An inherit shortcoming of PAPI's and VASI's is their lack of information with respect to the degree of diversion. In other words, how red is it? or how white is it? are not helpful questions. You can know that you're seeing 4 reds and know that a correction is required but they give you no information about the seriousness of your diversion or in other words, how far off from the intended path am I.
Just an observation. An element of the many which might help understand the lack of a timely response.