"Enemy footsteps are barely audible."
I've noticed this as well. The volume should be increased when they get within a certain distance of you. Some people don't always play with headphones and there can be a lot of in-game and real life background noise sometimes that drowns them out. I recall Battlefield 3 had a nice system where fast footsteps became more obvious when they were within 15 feet or so of you. So you could still be stealthy, but needed to be much more careful and crouch walk when you get close to people you don't want to alert. Battlefield 3 is such a well designed game, and I think it really only gets overshadowed because 4 had longer support/more maps.