She always enrages on the 4th ground slam. That's about 80 seconds for 110K hp. Not unreasonable. If you're lucky you'll last another 15-20 seconds. If you're finding it too hard to DPS, have everyone stand in melee range so she doesn't bounce around much, which will also allow the healer to drop an AoE heal and then DPS a bit. She doesn't hit hard so if you're finding your DPS to be a bit slow, have your healer help out some.

It happens. Occasionally Jindo's ship just become immune to damage. Only thing you can do is reset the instance and try again. Frustrating for sure, not much you can do about it however.

I've had it happen before - it's extremely frustrating because of the level of trash you have to clear before him. The only thing you can do is reset the instance and hope it doesn't happen again.