A well built 26 inch mountain bike wheel should handle the loads you described and if you have 135 spacing it will be plug and play... you are going to get a hub that is set up for 8-9-10 speeds and not your 7 (which will require a spacer) which will also let you upgrade your drive train if you so choose.

A rocky trail is nothing compared to the big drops and abuse an mtb wheel can be subjected to and the XT / Rhyno Lite / Dt Swiss combination is a solid one... the Rhyno Lite has always been a favourite rim and I really like the Mavic 719.

A well made mtb wheel will stand up to an immense amount of use and abuse... I know some big guys who do some pretty bad things to their wheels on the trail and if the wheels were well built they hold up very well.