almost every experienced heroic multiboxer will tell you the tank should be JC/mining or JC/BS. There are a lot of good reasons why in other threads, enchanting is a waste and insanely expensive to level. As a starting tank the benefits of the JC-only trinket and 3 prismatic epic gems is unbelievable.

Eng is good for the helm, but once you get a better helm, well then eng is fairly worthless. Whereas until at least the next major content patch JC will always be great no matter what gear you get. Mining is great for the +50 sta boost, BS is perhaps slightly better (scales better with gear, 2 extra sockets) but insanely expensive to level and there are no BOP self-only BS enhancements other than the 2 extra prismatic sockets (+48 stam basically, same as mining, or +32 defense).