My recommendation with act 3 is to split it up between multiple playthroughs. If you're like me and care a little about the roleplaying aspect, just do the things your PC or party members would feel important. I'd spent a long time and made some decisions I personally wouldn't have made if not for keeping with my characters' story; it didn't make sense to me to go hunting down every nook and cranny of a huge city while it's on the brink of destruction. There's just too much to do!