Considering your usage, you need tyres that offer good wet grip and are also durable over rough surfaces.
To begin with, Goodyear Asurance Duraplus would be a good option. This tyre comes equipped with DuPont Kevlar technology that makes it durable over rough roads. The traction and tread life on these tyres is quite good as well.
In case you want tyres that offer better grip and comfort, then go for Bridgestone B290.
Also, since your vehicle runs fully loaded, as mentioned by you, I would recommend that you buy tyres with load index suitable with your needs. The load index should be equivalent or higher than the stock tyres (company fitted tyres )