We did a 6-month / 34000km trip to Australia on a DL650 with my girlfriend, and I must say I´m quite happy with the way this bike performed 2-up, while practically overloaded. It is in fact exceptional in this class (being only 650 I mean)... I used to ride Africa Twins in the past, never had this much load on any of them, and still their driveability suffered more. The frame and subframe of the DL are very strong, and the engine pulled the load surprisingly well.

Sure its stock suspension could use some tweaking, but I´d also be careful installing some fancy multi-adjustable stuff, that might give up without proper maintenance. Stock items arent perfect, but generally they´re pretty good in taking the abuse. There wasn´t much ground clearance left (as there isnt much to begin with!) but it turned out to be only a minor problem. Naturally the routes you choose to go to, will dictate, how much offroad-ability you will really need.

To be honest, our bike, with this load, was almost impossible to ride in deep sand or mud, but luckily these were quite rare, and only encountered them in short sections, that we were able to ride through. And I´m not so sure, if there´s any machine, that´d be so nice to ride in real challenging terrain with this much weight on board. So personally I´d concentrate on the bike´s technical reliability, its ability to carry the load without failures, and being comfortable (for both rider & passenger) to ride long days on tarmac, or good condition gravel.