ok so we have blights and whatever the lichs minions are for basics, for actual NPCs who matter we need a Druid Spellcaster vamp, Female barbarian Vamp, The Lich, and The Noble Vampire
Alright then you have time. I suggest rolling each in game hour to determine if they encounter blights and survival/perception checks to determine if they see it coming, if they get jumped, whether or not they get the chance to aviod
let them make these rolls
Is this a group that prefers hack and slash or story sessions?
sure that sounds pretty fair to me and they have to camp at night to, if they travel at night should i up the rolls of encountering the blights? they're pretty 50/50 when it comes to it.
on the return journey half the chance of encountering blights
on each encounter roll a d20, increasing the case of the vamps finding on each encounter
all 3 at once
Do story stuff with the forest dwellers on the way in
on the way back, the vamps attack
So the vamps by themselves are enough XP wise id give the Warrior Vamp 3 levels in Barbarian same for the Spellcaster Druid in addition to everything else they have
For the player characters, might I suggest when they roll for health, its whatever they roll plus con modifier or whatever slightly higher then half plus Con mod per die (so 4 for a d6, 5 for a d8 6 for a d10, 7 for a d12)
so they guarantee have the health needed
but don't feel like you are cheapening the experience with full health