Lemming42
Arcane
1) Break the wall to the temple from the outside, where the drunk guys are sleeping (you generally have to knock the drunks out first)you can't kill all three leaders stealthily (hobgobbo will turn every1 hostile no matter what)
2) Send your best stealth character in through the hole, and have them sneak along the rafters until they're overlooking the warlord
3) Send your best melee fighter in the normal way. Knock the two merchants on the platform out when the goblins aren't looking, then steal their explosive barrels (or just get a load of barrels from the secret room).
4) Place two barrels next to the warlord, on his right-hand side.
5) Have the entire party except for the stealth character leave and wait outside the hole in the wall.
6) Have stealth character detonate the barrels. Warlord is either killed in the blast or thrown down the nearby chasm.
7) The goblins freak out, but can't see you yet. Sneak away fast before they come up to investigate, then leap from rafter to rafter until you're back at the hole in the wall - there are no guards directly in your way
8) Rejoin the rest of the party and escape up the side of the cliffs.