For simplicity, assume JC is the best for tanking, DPS and healing (which it is).
The second primary profession depends on what you want. If you occasionally DPS, want to PvP, or need avoidance gear, you'll want to get BS instead of mining. If you only tank, will never stop tanking, and see no reason to ever do anything else, you'll be fine holding on to mining.
Also, only a true min/maxer...



