The barell is at +12, -5, -210 (not +210, which doesn't exitst).
It is on the ground to the right of the forge against the wall.
The pitmasters are all heroic - one a group of four and several single heroics - they are in the room with the puddle of gunk (-80, , -146). Which is up the coridor from the quest barrel and left at the 'T'. One or two pitmasters wander the coridors as well.