If you're careful on pulling undead in Bloodmoon keep duo was pretty nice(mobs have like... 120kish hp tho), these come in packs at most of like 3, should be fairly easy to self keep them rooted or atleast one VP'd away.
there's also a graveyard in hills of shade with undead, undead villagers to north east(Fishers and such, they turn undead graphic when like 80% life, can slay at 100% tho), and an elf village to south west (turn undead graphic when dmg'd like fishers, this one is run change immune[no root/snare])
Loping plains has the undead near hills of shade.
Shaman solo could prob Root-rot in like every zone but the rune speed immune ones, most zones I've been to only have named as summoners, Paladin solo you're probably better in like FC, although Loping Plains undead and atleast Graveyard/north east Hills of Shade undead should be doable as well.
If you get in trouble soloing em you can always root, and back up to heal/med as they dont summon.