If it's ok with you I'm going to give it a little more than two games to make a call on a guy like Meaney who from what I've heard was stinking it up in reggies until a desperation call into first grade. Nichol-Klokstad is doing ok in attack, is defensively suspect and, again, has virtually no experience.
Personally I think Mbye is decent and probably playing injured at the moment.
I'd group NRL fullbacks as follows:
Superstars: Tedesco, Trbojevic, Ponga and Tuivasa-Scheck at a push.
Very good: Gutherson and Moylan.
Good but limited/inconsistent: Johnston and Dufty.
Mediocre: Boyd, Gordon and Te Maire Martin.
Too soon to tell: Jahrome Hughes, Nichol-Klokstad, Watene-Zelezniak, Meaney.
Fully fit, I think Mbye can be in the second group and even now his defensive qualities mean he's probably got more value than a Dufty or even arguably a Johnston (who is massively flattered by the team he plays for). If all those last four turn into really good players I guess Mbye could end up being in the bottom half of the comp, but I think it's more likely that he's around the middle with lots of up side given he's probably playing at rather less than 100%. That doesn't wildly excite me but on a reasonable contract (which we think he's on as the Dogs are paying some of it) that's a pass mark for the Tigers.