not agree in your affirmation that sorc-necro2 isnt good, probably is the best rank 5 filler for necro 2… u can add another summon to your army at bosses or when u want, and cat buffs are awesome for necro flesh cannon aoe+5 (flesh cannon really apreciate the aoe) +sp regen… and not only for u for all your party.
The other option is linker 2… just for add 2 links more and spiritual chain? not worth in my opinion, the good buffs are given by healers and there are times that u are overbuffed so spiritual chain isnt awesome ,and i said only 2 links more cause in a prty with a blssing u skill is level 6 so is 6 links or u can get dandel gem 6 links too.
Other rank5 fillers are just bad at c1.