Volvo doesn't really make ANY car for off-roading, NOT even the new XC-90. That might be considered an SUV but it's still not tough enough to handle true off-roading like a Jeep (for example) in comparison.
Whatever you do, don't buy an V70 XC thinking that it'll be better of rough roads as far as durabilty is concerned. It's no tougher than your present V70.

I'd tend to agree with your mechanic in that if you insist on driving on rough roads or off-roading trails, etc....get a good SUV or 4WD PU that's truely made for rough roads.

Volvos are good on normal roads but not ideal elsewhere. What IPDs oil pan protector STILL doesn't protect is your equally vulnerable radiator which hangs low just behind the bumper. Those get damaged easily, often by high curb stops or ice mounds in winter.