In regards to Fifita I always felt personally that he is better suited to playing in the 13. Freedom to roam in attack and play what's in front of him and defending up the middle. I think he gets found out by guys like Isaako who have footwork and speed. Tino can hold his own more out wider in defense. Other than a better hooker that really is the only change I would make to the forward pack.
As for last night Holbrook should have given Fifita a rest. TPJ did a number on him and you couls see Fifita physically hurting midway through the second half. A 20 minute break for him at the start of the second half before coming on for the last 20 could have seen Fifita have a bigger impact in the outcome of the match. Broncos made a similar mistake with Haas for a while, constantly playing him for 80, it dulled his effectiveness. Just because you can doesn't mean you should.