Because B****** love cannons. Is it a meme build? Yes. Will it be outperformed by halos slop, ROB, or skill duchess? Also Yes. Is it fun? Yes.
This is a meme build of the highest tier, youre basically a liability for your teammates. You can't take one iota of aggro and all you do is hide in the corner of the map and blast everything in the general vicinity of the enemy.
Survivability? Hope youre good at using the duchess restage invulnerability because you will be spending 3-5 business days slapping the top of that cannon per shot.
Fun factor: Big plus here as you knock down or micro stagger just about every enemy as well as enemies that can be staggered from an arrow to the face. Even draconics must respect the raw fire power of a ballistae.
Damage: Surprisingly not bad and really shines on certain enemies and flying/mobile types, try to free aim headshots for bonus damage. However you are truly at the mercy of RNG for your dmg. (more on that in a sec)
As Jarcannon is the only purple in its class, its very consistent to get with dormant power find ballistae, all you need for relics is physical damage and cool down reduction for restage and restage invul.
Gear to look for: Majority of drops are now worthless, Physical attack or attack up on full hp, thats all you get. Maybe an occasional projectile drop off reduction but RANGED ATTACK DAMAGE DOES NOT CONTRIBUTE. For whatever reason ranged attack up provides no benefits so feed that to your iron eye.