It seems more users are tagged as anonymous in the Schema:Edit instrumentation than are actually anonymous. Of all events, 78% have user.class = IP. Of all saveSuccess events, 57% have user.class = IP. I looked quickly to see if these percentages change over time, and I didn't see any significant change.
UPDATE: Analytics needs to analyze in depth exactly what's happening in the data, as the Editing team does not know where to look for problems. The code they use seems simple and some unexpected user behavior might be explaining this data (for example, a lot of people logging in during their edit).