On the PTR prepatch Shadowfang is indeed dual wieldable. I think only the blacksmithing items were kept as mainhand and all of the lower level itemization changes still apply from day 1.
I have 5 level 19s done now (Rogue,Pally,Hunter,Druid,Priest), 4 with naxx enchants. Probably going to make a shaman during prepatch, possibly a mage or lock as well. Then I was considering a 39 in BC eventually once I get situated on the main.