I've played ALOT of ballista.
As Rdm, BST, and BLM.
I've fought many opponents. 1 on 1 and in parties.
And the answer to my own question is simple.
It depends on the job your using to fight with.
Nin is almost impossible for me to kill with my BST, but for my Rdm, he's a chump. <== Yes I mean chump. (sorry nin's but it's true.)
Rdm, is very difficult for me to kill with BST, but for my Rdm, he's a little easier. Rdm Vs. Rdm just come's down to gear and skill. I honestly can not recall 1 time I've ever been beat by a Rdm. Last fight though wasn't really fair. 56 rdm vs me in a 60 cap.
THF, for my BST Thf is a chump. Even with shadows a thief does not stand a chance against a BST. He can't outrun the tiger, and he can't outdamage the dual axes. Most I've seen a thf do is sleep my pet and flee from me. Then I just follow him as best I can. Few sec's later my tiger come's zooming by. Then I follow the tiger, who is probably asleep again. 1 trick though is to reward your pet. like once every 2 min ><. But if your pet has Poison or Dia on him.. Thf can kiss his @zz goodbye.
For my Rdm, thief is a pain. Gravity and bind is resisted ALOT for some reason unexplained to me. But if I ever catch one which sleep, or sleepga (uncapped.) He's pretty much dead. One episode I remember is fighting Lester on the Titan server. Great theif, and last I check the score was 3 to 2 him.
PLD, is a real ballista chump for both Rdm and BST. I love to aspir the crap out of them. If I'm in a good rumble with many char's I don't attack pld. I like to keep them around for when I need MP to kill there buddies with. Generally in a rumble pld's are ignored b/c they don't do alot of damage, and they have high def. So they get slept and suck dry, then let loose.
Whm is a breeze for Rdm but a little tougher for BST.
And as far as fighting with my blm... He's only good for sleepga. Aside from that, I just grab petra, stay away from the fight and score. Good for croud control and finishing up the fleeing enemy. I get the most petra scored as a blm.