Looking to change classes, what do you suggest?

[Aistaraina]

Is it because of their big amount of damage?

Other DDs (okay not ARC) can match up to LNC, but the ease at which LNC can put out the numbers is why it's widely used. We've had PGL on Ifrit, and they work their ass off but can compete in numbers. But it's the same as the 1.18 ARC frenzy for DH. Come 1.20, something else will be the norm.

When going solo, how well does a LNC do?

You're better off with MRD for 1v1 soloing.

Can you take up on many mobs at the same time easily?

lol