If you can’t fit Discs, which are the preferred option, Magura HS33’s are a good alternative over V-brakes. Have been running the Front Disc (Shimano LX/XT) & HS33 2011 model rear on rigid for the last few weeks in very muddy conditions, and the pad wear hasn’t been much worse on the HS33’s than on the disc.
Looking at the NX 8.1, realistically, your best option would be to either live with the brake wear, or save up and get a new bike, as putting money into the NX 8.1 will false economy.
Bikes have moved on since that was released. For the cost of replacing the fork & brakes with mid level ones, you could almost get a new (last years model) bike, take a look at places like Pauls Cycles for an idea of what there is around