These days, if your pack is merely competent at making metres and resisting big props early in a game, their main job is to defend their line and create opportunities in the opponent's 20.
Sadly for me, the Sharks have had one of the best packs at making metres and restricting opponent's hit up metres for years, but it doesn't count for much. That's why the loss of two great props but the gain of some halves, a good hooker, and hopefully a centre still to come... is a great trade off.
With two refs and the rules so stupid, penalties play as big or a bigger part in getting the territory to be in attacking position, and the wrestle, offloads and hole running are more important near the try line. So the big men are just not so valuable (except Matt Scott, he's a gun). It is a sad indictment on the game that Gallen, bloody good as he is, is one of the best "props", having virtually no experience as a prop and not being very big for a prop. Big men have been taken out of the game.
On the other hand, Manly's pack with merely competent props and a good hooker, has been the best for years at not missing tackles at crucial times on their line, and at setting up attacking play (mostly G. Stewart in the "blind side 5/8" role good locks/back rowers can play, and Watmough with his running).
The Broncos have also been good at resisting opponent's, and guarding the fringes of the field defending their try line.
So a good pack is a balanced, pretty mobile pack that doesn't miss tackles. For mine, that is still Manly with the best pack.