Yes, the Nashville Predators did overpay him in both term and cap hit, but Sissons is worth it because he can do it all on the ice.
He can play on the wing and at center and kill penalties, he can do basically anything that Peter Laviolette asks him to do, which is absolutely great to have for the next seven years.
Sissons is still only 25 years old, so the contract will run until he’s 32, basically meaning he will remain a Nashville Predator for the rest of his prime, barring any trades, but even if there needs to be one he is on a very moveable contract.