Originally posted by vinyblaster:

I always thought cave doors would behave like the ones in crypts and not yield any iron.

As for your main point, I agree. It is an odd game design decision that only 1 boss ends up being a hard stop to progression. Almost looks like an accident and devs never anticipated how the other ones could be bypassed.

You don't need black metal weapons/gear to survive the Plains.
I would think, like most of the game already, that you only need the last zones gear to progress into the next.

Since there isn't a next zone to progress into yet there really isn't a need for it yet. Not sure they will change that though? Or maybe the mistlands gear will not be awful to get? Like black metal drops from enemies that are plentiful. That might carry on to the mistlands as well or something in the mistlands may drop some tears?

Hard call to make honestly as being unique in its workings isn't a bad thing either.