I watched the replay with a current first grade prop. His comments : - "We were bitched". He lives and breathes the dark arts and as a current practitioner he is well placed to make an valid and objective assessment.
Not a lot of hooking in the modern scrum, particularly from the non-feeding team. "Tightheads" should be more accurately referred to as "Scrum turnovers", and are usually the result of a flaw in the technique of the whole scrum, like a ricochet, or a kick through from a second rowers foot or the like. Not indicative of a bad show by the Hooker.
Weight difference - Meh. When the 135kg fatty came on for The Darkness, their performance actually deteriorated. Size isn't everything. Many on this site have bemoaned the lack of some decently sized piggies with some mongrel in them, however I doubt that selecting a big Australian Bullock like Jack Bowditch, solely to get some weight into the forward pack, would have made much of a difference.
The Darkness based their game plan around set pieces, and appeared to have focused on that at training.