What is Machinist identity?

really is it gun job?
which gun?
multiple guns?
Bazooka big and slow guns?
or machinist using robots to do explosion?

I think Machinist can be 3 jobs:
1- Light wight gunslinger: using light wight guns that do fast attack like viper. (DPS)
2- Heavy wight Bazooka style job: using hard hitting sniper bazooka or something slow but hard hitting job. (DPS)
3- An actual machinist who use only robots to tank damage.(Tank)

sage is kind of machinist of it was healer too

what do you think machinist identity is?