CR ratings for the final encounter are way low. Putting mobs with that many Immunities and Resistances makes the encounter impossible for lvl 4 PC's. My table turned and ran. They took the hint.
After the mod was over, I told them what they ran from they all immediately said CR 2 for the mechanics was radically different than what they should be. Given all the immunities, there where only two PC's that even had a chance of injuring them. The cleric -COULD- have spammed sacred flame, and the monk -COULD- use the short sword they grave robbed earlier in the mod to do minor damage to dent them. But by the time they would have figured that tactic out they would have been TPK'd.
Anyhow, the result of the table was to abandon the miners and head back up for 'reinforcements'.
Ooze Jumper the Ineffectual
Mourner's Public Relations Specialist
Frustrated Undir Bounty Hunter