[Thrasher91604]

I had already forgotten about the tarnished sentries...

Not sure if magical piercing weapons will work, but non-magical piercing weapons will not work. Magical blunts work, as do magical slashing (to a lesser extent I believe (EDIT: hmm, not sure if this was the case for the sentries or the iron golems)).

Having meat shields for the sentries to attack to take the heat off your characters helps a lot.

You can still sneak past the salamanders, and when you run into a sentry, it may cause a call to arms with the nearby salamanders, so I recommend sneaking anyways to find lone salamanders and lure them back to the party after coming out of shadows. Then when you come across a sentry later you get fewer or no salamanders with it.