For those saying JC/BS for the extra gem slots - I was weighing in between JC/BS and JC/Mining on my tank and I chose to stick with JC/mining.
Besides the fact that mining makes more money and the ore is useful for JC also, the extra 2 gem slots for BS seem better than they are. yes, they're fairly flexible, but if you compare them to the +50 stam you get from mining they're not that great. Blue stam gems are +24 stam each, thats +48 stam for both slots, whereas you get +50 stam for mining. True you could use some other gems in the BS gem slots but for a tank I just don't think the benefit is that much greater.
Now, once epic gems are highly available maybe things will change but for right now I would take mining on a tank over BS.