Jett has about half the DPS of most other classes with similar range. Its not nearly bad enough to be unplayable, but it is definitely in need of some re-balancing. If it was on the damage charts it might be at the bottom, but I'm not sure how Beast Tamer's DPS compares to Jett.

Starforce Salvo, a Jett's main bossing skill, is heavily dependent on RNG because it has a final-attack like skill which only activates at a 2% rate but deals 10 * 355% damage.

Grinding levels isn't too bad once you get decent equipment. I'll go over the three skills I use the most.

As mentioned by ChippyTick, Starline Three does more damage than Starline Four. However, I think in most maps, Cosmic Upheaval is better at moving monsters than Starline.

Backup Beatdown is better spammed than used as a keydown skill, which is a bit hard on your fingers. It has a bit of an awkward hitbox. The keydown portion of the attack has a very small hitbox, much smaller than the animation would make you believe. Releasing the key results in an attack with about 2 * 800% damage and about twice the range the hitbox suggests.

Cosmic Upheaval can drag a ton of monsters to directly in front of you, but is a bit glitchy; it often doesn't work as effectively if other people are in the map, monsters will often move back to their original location after its used.

Finally, Jett has no party buffs, no binds, will never receive re-balancing when its needed, and might not even get fifth job on time.