you only need undeads untill lvl 44, after that you get inquisitor and you can get to 44 easily by nuking around execution ground then moving to dragon valley
ruins of despair and ruins of agony near gludio are 20+ undead mobs if i remember correctly... after that, execution grounds near dion and dragon valley from 40ish onwards?
For Solo play Bishop:
LVL 25 - 35 Execution Grounds top floors. (DU)
LVL 35 - 52 Entrance and field Dragon valley (DU / MoH)
LVL 52 - 68 Dev. Castle area (Inquisitor / MoH)
LVL 62+ Ancient BG AOE in Inquisitor mode
LVL 68 - 80+ Rift (TU)
That been said, I think once you have learned inquisitor skill its better to go to normal field area's where mobs drop herbs.
Without recharger you'll have a lot of downtime hunting undead only b/c they dont drop herbs.
Maybe pickup a MP pet too and raise it with you. Will help you a lot if you still wish to hunt undead's.