Depends on what you would count as "viable", he would still have decent survivability through hes 67k shield, but you do not gain much damage by using a 2-hander compared to 1h+shield.
But you can dual-wield, it is what i would recommend you to do if you want to gear an Engineer in Darkness Falls, go for the Residual Aftermath set, great survivability and when parry procs you can get up to 160k absorb shield from aegis of fate ^^, probably want to use 1h+shield during the gearing up process tho.
Have not tried cannoner in DF so no clue about that tho, but the cannoner abilities are not all that impressive, also when i geared up my Engineer i used the Adamant Set since it had great stats for the engineers already great defensive abilities so i dont know how well 2-handers work in DF with Engineer, did test it way way way back, but i dont remember how it performed.
For a 1h+shield i would go with this build: http://tidbi.ru/eng/engineer.php?lvl=100&fm=33&skill=000F00F0E0F000000FF1FF0000F0F0&stat=apafafdUaaaaaaac
Shield Bash is the best ability when it comes to building charges, does it really fast, and later on you wont even need it since your autoattacks builds you max charge in 2 seconds, Emberquake is the best ability the Engineer has, nothing else does more damage and it is also AoE, still 15 points in super charge since if you slam emberquake in the face of a target it apparently counts as a melee hit for some strange reason (and theres not much else to put points in that is any better
), Onslaugh works on bosses, so maxing that gives you much more than using storm burst, its also a great ability to get in or out of a fight ^^