Hey there! Before I continue, I should mention that I managed to solve this issue on my own, but this does still need to be addressed.

After accepting the quest "Skullduggery", I went to the location of the two Sahagin NPCs that should have spawned in the designated areas. They did not spawn. I had tried resetting the client to no avail and abandoning and re-accepting the quest.

How it finally got fixed was completing every other Sahagin Beast Tribe quest I had accepted, then abandoning and re-accepting "Skullduggery". At that point, both Sahagin NPCs spawned properly.

I just thought I would let you guys know that this may need some looking into.