When you compare a BST/NIN to basically anything else, they get trounced
I was leveling BST for 2 reasons:
1) Because I wanted BST as my main job
2) Once you get BST to 75, you can go xxx/BST and solo the entire game with all the jobs.
I have seen some BST win in ballista, but it is on rare occasions. Any good SAM/Nin or Nin/War or War/NIN, I have even seen, a WHM/NIN kill a BST. But that is probably THE best WHM in the entire game, on all servers combined, as far as PvP goes
That same WHM defeated a War/Nin and MNK/NIN, she was beasty.