I don't really know anything about Forlorn, so I'm asking this out of genuine curiosity
Original post suggests lvl 12-20, does this mean that goblyn's are on par with demons/devils and even salt shadows/void spiders? It's possible that my understanding of these creatures is skewed, as I see them as threats to x lvl character, which perhaps shouldn't necessarily be the case. However, it just seem silly to me to think that goblyns would ever equate to the danger of a handful of pit fiends, or a mob of salt shadows. That being said, there's power in numbers. You could of course give them things like a high AB an debilitating effects like crippling strike so that while alone they're no threat, in large numbers (as I seem to undestand there are in Forlorn, from this thread) they pose a significant threat.
Of course, now I'm just talking mechanics and I'm sure most people who are interested in this don't care too much about that. Personally, however, I think there should be some sort of balance struck when considering these things in terms of their difficulty and how they compare to other encounters already present that could/should present an exponentially greater threat.
Having said that, I love the idea of new domains; and I believe that the lvl 12-17 characters could really use some love in terms of dungeons availabe-especially now that Perfidus is only accessible through the mists. With the recent updates to Hazlan, this seems a very plausible and interesting addition.