During my initial attempt to complete the GOW 2 PS3 collection game, I found that the trophy for Boss Batch 3 did not unlock. I completed the game 3 times over and still no trophy. I found a posting on this site that explained how to fix this issue but did not make the attempt to see if it worked because I have found other glitches that I wanted to work out first. In doing so I found out by accident that when you play GOW 2 fresh (like you just bought it and started your first attempt at completing it) I ignored getting any of the URN's just 2 see what would happen. Once I killed the last sister of fate, I was instantly given the Boss Batch 3 trophy.
I would have to say that those URN's might be the main problem for GOW 2. Can not be sure, but my experience so far points to that.