The NC and Mumble are just helping to organize big alliances, its not the cause. The alliances were there before NC. The problem of not making an alliance is a huge ammount of discipline that it takes. If one gang has 12 members, for the two other gangs, each having 8 members, its a great task not to ally with each other, knowing that in 80% of the time they meet the strongest gang, they will lose.
The right way to go is adding more key places where players need to interact and can do some serious PvP, like HQ mines are now. TC will always be about full scale war, and I think its allright, its fun when done once or twice a week. Lets say that once the city is taken, it cant be retaken for 5 days. Boom, TC is off, its time for some small scale action, like guarding/PK in the mines. Hopefully devs will add up more location-based requirements for crafting&gathering like HQ mines&waterworks&SAD are now.