My druid was able to complete this quest today with dubious faction. Completing the quest gives the following faction changes:
Katta Castellum Citizens better
Validus Custodus better
Magus Conlegium better
Citizens of Seru worse
Seru worse
Shoulders of Seru worse
My druid was still dubious after completing the quest, so the faction change doesn't seem to be that great.
Even back when Luclin was new, the Earth Blessed Mantle was usually not worth the effort it takes to acquire it.
The EBM sells for a little over 9 plat when sold to npc vendors.
Kamgar