Hi, Jon!
First of all you have to look at ConceptGuide - is there ExtremeEdpEntry.
In EXOS_ConceptGuide for 15.4 there is only extremeEdpTable, extremeEdpNeighborTable and extremeEdpPortTable.
In MIB file there is a lot MIBs from ExtremeWare, so they didn't work in EXOS.
Thank you!