I used the word awful to describe Tuimavave's season, and yeah that word might be a bit harsh, but I'm judging him by his previous standards which have been very high ever since he joined the club. Statistically he might still look ok (although regarding errors, how many times has he caused an error that doesn't go against his name? The offload to Lane for example). His workrate is still very good, so of course he's going to have decent yardage stats etc. I'm more concerned about his poor defensive reads, or how often he gets caught flat footed these days, or how he isn't running the smart lines he used to.
Lots of centres get to the point in their careers where they just aren't dynamic enough to play the position anymore, and the logical move is into the back row. I think that's where Carlos is right now. A backline of Swift, Sutcliffe, Scott and McIntosh with Tuimavave, Savelio and Fash in the backrow could do really well imo.