I intentionally avoided reading through the Bestiary because I wanted the fun of experiencing monsters for the first time. I remember spending my free time reading through the Monster Manual and knowing exactly what to do as soon as the DM started reading the description. So, maybe this is partly my fault. But I seriously never expected something like that to be thrown at a party of level 3s (especially a party of 4 level 3's.)
Forgive me while I whine for a moment:
What's your average martial class look like at level 3? 33hp with 14 Con and their favored class bonus to HP, and 22 AC? A d8 is looking at, what 27hp and AC18?
Melee: 2 Slams +14 (2d6 +7)
DPR against 22 AC = 22.6, Against 18 AC = 29.5
The rogue, bard, inquisitor, magus and monk are dropped unconscious with the _expected_ damage output from 1 full attack. The fighter is 2 points away from permanently dead in the expected damage of 2 full attacks.
How likely is it that the fighter goes down in 1 round? 10.8% Almost 1 in 9 times you'll KO a full hit point level 3 martial character in 1 round. Then add the fact that the monster doing the hitting has DR5/-, AC 18 and 68 hit points. That fighter who is expected to live for two rounds is swinging, what, a great sword at +7 for 2d6+11? Expected DPR something around 10? OK, I can see how a party with a pair of 2 handed, well armored martial characters and a couple other people capable of doing a little damage will be able to beat the encounter, but there's a high probability at least one person is getting KO'd and very easily killed. We had a knife master rogue (oh yeah, no flanking on this guy!), a dervish dancing bard, a tankish cleric with a warhammer, a non-tankish cleric with a scimitar, a life oracle and a wizard with control spells. Both clerics died (my cleric took a total of more than 120 points of damage, the other cleric got killed outright in 1 full attack action.) Were the characters badly built? None were probably worse off than pre gens, but the group makeup just couldn't handle this encounter.
Is that a reasonable step up in encounter difficulty from goblins that can only hit you on a natural 20? Maybe it is, but it would be really nice to have some forewarning, or build up more gently.
Math: Probability (1 round KO) = P(2 hits >= 33) + P(1 crit, 1 miss >= 33)*2 + P(1 crit, 1 hit >= 33)*2
= P(0.4225*0.09722) + P(0.011375*0.09722)*2 + P(0.0325*0.9901)*2 = 0.1076
P(4d6+14) >= 33 = 0.09722
P(6d6+21) >= 33 = 0.9901
(Gotta love Wolfram Alpha)
</rant>