Nissan Navara: Harsh suspension

The suspension on my 2010 Nissan Navara SD22 dual-cab is really harsh on anything other than smooth bitumen roads and as well as being uncomfortable to ride in it will eventually shake the vehicle to pieces. The Service Manager at my dealer says that the suspension is naturally firm on this model, but when I took it to Pedders they said they get a lot of this particular model in for upgraded shocks and suspension and that it makes a big difference once it's done. In addition the original Bridgestone Dueller tyres will need replacing by the next service (40,000 km) which is a very short life span considering the sort of driving I do and what I normally get out of a set of tyres. Have you had any experience with these problems on this model and do you reckon I have any call on Nissan about this?