IMO Talakai should be considered to be there or there abouts. Has been a quality performer on a weekly basis, with Holmes being the dominant THP the Reds don't lose much when he comes on. Probably gain a bit more around the pitch but certainly no less at the set piece.
To be fair both Roberts and Taavao have been starting for their team. Talakai hasn't started once and his minutes have been way down. Can't see Cheika picking specialist reserves.
Unfortunately I don't think Sam has played as well as in recent years either. But that's probably a result of the minutes thing.
I think, at his best, he's close to the next best 3 but I wouldn't have him in the squad now.