@fredchuckdave: I got like an 80% completion on the game so I don't see how that was a speedrun, but whatevers. I just didn't find the tomb puzzles interesting so after the first three I stopped, and most of the collectibles are pretty obviously on the main path of the game and don't require much hunting around for. Especially once you get the perk that reveals it all. I just didn't find their audio log equivalents interesting to read or sit and listen to so I skipped past them when they popped. If I had of it probably would have added an hour or two to the game right there. Plus I had already seen the early cutscenes thanks to the QL on the site so I skipped them which was about another half an hour to an hour. So if you add that up that's closer to your time range.
I just think I blew through the combat quicker then most people. Based on videos I have watched of people playing it seems most hide around cover and jump around the maps but I never felt a need to. I was able to just stand there with my bow and headshot guys and take them out. The monster closet enemy spawning meant I could just sit there taking them out one after another as they spawned and jumped in the same spot as the guy I just one shotted. So combat scenes that I watched take 10-15 min for others were over for me in several minutes.