Thus far only May and Api have provided value from that list.
Luai hasn't gone close to his price tag. I don't know what Turuva is costing us, but I'm sure it wasn't cheap and his performances have been at best, mixed. Hunt has failed to either change momentum in games or play an increased role. Bird has had some good moments but was also dropped out of the team a few weeks ago. Skelton, I'm impressed with when he is on the field to be fair but has missed plenty of games.
Two of the Fainus are reportedly on half a million. One had a solid rookie year but has been awful this season. The other has hardly been on the field nor performed to his price when he has, though I think he will eventually prove a good player. Sione is probably playing above his contract but had a couple ordinary years before doing so.