I think that if Ek was placed in more of a top six two way role, much in the same way Couturier was, he would easily be worth this contract. However, if their plan is to continue to keep him in a purely defensive role, this doesn't make a whole lot of sense. I have no idea what the plan for him is in the next eight years, but at this point, whether or not he lives up to this contract is entirely on how the rest of the team is built and how the coach deploys him. Guys like Bergeron, O'Reilly, even Danault, etc all carved out careers as strong defensive forwards playing on an offensive line. Now Ek needs to be able to do the same.
As a player, he's worth this contract, but for the role he's currently used in, it's a bit much.