One of the reason Farne is lower use in DMM is because of Estelle, which is one of the reason of Summoner Class is to exchange Mages. The reason is because Estelle debuff all enemies MR by 70% (pre-SAW) and 50% (SAW) with Damage + AoE + Range multiplier which makes Farne job as change for Magic DPS significantly lower than her even if Farne has True Damage. It's true that Farne's heal is good but she isn't really useful with 35 CD in Majin particularly. The reason is because Units Ranking is based on Majin usefulness which make Farne isn't really good.