I didn't really like the episode.
It was just far too coincidental and plot convenient for my liking.
e.g.:
Army of the dead completely able to form ranks, use swords, follow orders, use intelligence, pull the dead dragon out of the water with chains but not a single one of them can wield a bow and arrow. Nah, they cant do that because then they'd be able to shoot and john and co on their little island getaway.
e.g. 2: "I'm a magical ice zombie king, here I have my magical ice zombie spear and I will use my incredible magic ice zombie strength to throw this ice spear so hard and fast at that dragon flying around to hit it first time and take it out with one shot. Could have thrown them at those guys when they were on their island but idk didnt feel like it."
e.g. 3:"i was taking a little ride along the snowy hills and i stumbled upon my nephew as thousands of dead things run at him, I'll ride over and make it just in time to put him on the horse and die in his place. yeah, sound plan."