They were all un-signed at the end of the season so would have been available to sign T&T contracts.
Herbert seems a waste to me. Theres the point that we can sign as many T&T players, however I would hope that Herbert isn't prioritised over the development of Max Taotua or Tino Tavana. Getting one of the players I mentioned may also do that, but those guys all have recent NRL experienced and development upside. A 28 year old injury prone player who hasn't played in 3 years really does not have much, if any upside.