This reminds me of the 3-13 module. The sinspawn were pretty easy pickin's, then they hit you with a BBEG that seems ridiculously over the top: A level 6 Ghast Cleric with ability scores 17 or higher...getting +12 to hit, three attacks, and +8 on damage per attack and paralyze/disease rolls for each attack? lmao.
Admittedly, though, I think we're understaffed for this mission. If we were all level 3, we'd probably withstand 1 or two round of attacks and hopefully we'd be able to do 64 points of damage with three guys in melee. But it looks like we're only going to get two melee attacks and we're running for our lives. Also, if we had a level 3 caster, divine or arcane, it would probably even the odds some.
The reality about PFRPG / 3.5 is you have to get the rolls. Had Ransom been missed, he adds another 4d6 worth of damage. That's about 14 points...puts the creature down to 23 and very kill-able in one round. Alternatively, if I could have hit a couple of more times, the creature would probably be in the low 20's.