What difficulty are you playing on?
If it is PoTD, it looks like this zone has been affected by the 3.1 PoTD difficulty change. Before it, I had a run through this zone and as far as I can remember risen creatures had 1-2 skulls (+1-2 lvl) for my lvl 8 party. If my suspicion is correct, they could just forget to update the quest level restriction/description.
However, it is still possible to finish this quest at lvl 7-8, there are several tips how to fight enemies in Hanging Sepulchers that might be useful:
- Don't use weapons/spells with piercing damage, all risen creatures are immune to it. Blunt damage weapons (scepters for ranged chars, maces/warhammers for one-handed melee chars, morningstars for two-handed) should be quite effective against them.
- Use weapons/abilities with high penetration as risen fighters and especially champions have high Armor Rating, even more on PoTD difficulty. The weapons mentioned above all have both decent Penetration and 1-2 damage types including Blunt damage.
- In a fight where tons of small skeletons appear, consider using heal-on-kill pets (like Abraham) and spells (like Crusader's Triumph), they will provide a big amount of healing that can help survive high ST damage from risen fighters/rogues and AoE damage from risen mages
- In a fight with traps there are small passages which you could block with your melees/summons to keep ranged characters relatively safe and place the fire wall before them so that enemy melee fighers will have to stand right on it to deal damage
- In a fight with Dargules/Rotghasts, focus the Dargules first as their vampirism is very irritating and can be hard to overwhelm when your party is out of ability charges. Your tank could also get abducted by a Wraith so having additional melee off-tanks or summoning creatures right at the beginning of combat to keep enemy melees busy is recommended.
- Consider using characters that can summon controllable summons (like Pallegina specced into Herald class). You can use your summons to fight enemy mages in melee, then they usually stop annihilating your party with AoEs and start using protective spells/ST damage spells and become much less a threat. These summons can also be used to distract enemy melee fighters from your tank(s), so it is easier to keep him(them) alive.
- If you have Serafen specced into Cipher/Witch in your party, consider using Puppet Master, especially on enemy mages/priests. This can completely change the pace of battles as priests won't save/heal enemies, mages won't harm your party with their Arcane Dampeners,etc. If the enemy's Will is too high, you can greatly reduce it with his auto-learned Tenuous Grasp spell at first. Its cost is low, duration is decent, so even its graze can be sufficient to use Pupper Master successfully.