Goblin is definitely worth the watch as the story is very unique - I didn't think that I would enjoy it so much.
Despite the episodes being very long (which it didn't feel like), it really was enjoyable.
The low rewatch value is due to the fact that the episodes are 1hr and 30mins long, but this should not refrain you from watching it. I think it is a must-see.
I would rate the cast as 12/10... but you know it doesn't work like that.
It was really fun to recognise the references made about actual kdrama actors and even some kpop groups ^_^