I have a few thoughts after reading this. Saying that any submarine can outrun a torpedo is a misnomer at best. The situation would have to be perfect and it would have to be an older design torpedo. Otherwise the range of the torpedo, speed differential between torpedo and target, and the firing conditions make it almost impossible to do anything other than spoof the torpedo. A submarine is not going to fire and give away their position when the chances of hitting the target are low. Additionally the torpedo is guided by wire and walked silently out of the tube to give the element of surprise in most cases. The mk48 torpedo has an advertised range of 23 miles(38 km) at 55 kn(102 km/h). That could turn into a very long chase at nearly double the speed of the target. Additionally the faster the target goes, the easier it is to track it and harder it is for them to hear what is around them.
Additionally, why is the Virginia class submarine the fast attack submarine of choice for the game? Los Angeles (43 active), Seawolf (3 active), Virginia (7 active, 3 building, 30 planned but likely to be cancelled). As sad as it makes me to admit it, we can forget the Seawolf class but Los Angeles needs to be thought about more. The majority of the US fleet is the aging, slower, and older technology design of the Los Angeles class.
Being that this is a game about the arctic circle, thought should be given to inclusion of SSBN. I know that the developer diary says that they would not be put in harm's way, but this is simply NOT true. The location in the game title says that Ohio class SSBN as well as SSGN should be included. The whole fleet of them is likely to be in the northern pacific, northern atlantic, arctic, or tied to a pier at all times as far as the game is concerned. The value of hiding strategic deterrence assets as pointed out by the developer diary, use of nuclear surface blast/nuclear depth charge in naval combat, and positioning for first strike capability on land targets are all major factors in the SSBN field.