The priority should be the defense. That's it. There're more than enough forwards on this team that can make an impact. I'd say keep Hronek and Hughes on separate lines and pair them each with a steady and capable defensive defenseman. Graves and Severson make sense.
The fourth line could use a crash and bang type player, perhaps Milan Lucic to play with Dakota and Nils? He'll be coming off of his big contract, and could possibly be had for cheap.