I see the potential and a great setting but it gets dragged down by needlessly adding other aspects of the age of Sigmar. You could easily rewrite this story and not have the tzeentch sorcery plot and the story would be better for it. Then it would be a story of a down on their luck crew facing off a dangerous problem that might be lucrative for them.
In essence, the plot has this pirate tale or adventure at high sea quality to it. A mysterious blight that old crewmember share stories about, the doom of ships, what lies at the heart of the mystery is it gold? Is that by the numbers? kinda, but then again would it have mattered?
The aforementioned tzeentch sorcerer sets the story in motion but as I said you could easily write him out of it and he adds little to the overall story, he is not that interesting nor fun at all. Likewise, the skaven. they were kinda there and I never felt like they were a threat of any sort and this is something I feel is a problem with the whole skaven group in age of Sigmar, they are there yes but they are no longer the existential threat they were in warhammer fantasy. While all other factions have gained power through magic, sorcery or alchemist powers, the skaven have gained nothing. They are still the same and this story shows how outgunned they are both literally and lorewise.
I like the faction of the kharadon overlords but this series has been trying way to hard to make the story bigger then it needs to be, it would have been fine reading about adventures in the high sky without all the stowaways hitching a ride.