Pal 14 (oath of the ancients)What's their classes?
Wiz 13 (evoker)/Cler 1(knowledge)
Mnk 13 (3pp variant 4-elements)/Wiz 1
Brd 14 (lore)
Rgr 10 (hunter)/Cler 4 (war) [I might be wrong on the level breaks]
Rog (inquisitive)/Rgr (horizon walker) [I have no solid idea of the level breaks]
Also, they have good equipment.
Of course, at level 12, they took down a death knight that turned into a shadow walker (I think that's the name--CR 20 huge bipedal undead) when it died, along with--IIRC--4 devourers and 4 deathclaws (I did the encounter math after the fact and I think it was something like 7x deadly); no one died (though the rog/rgr dropped). When I say these builds would be speed bumps, I'm not exaggerating.