Who said Mechanic was nerfed?

I believed they were nerfed more on their early jobs (such as drill rush) than they were in 4th job. However a recent kMS update changed the range of some mechanic skills, so it's gonna be a long time before you see a Mechanic take down Zakum that fast.

As for the potential system, I think it'd be a lot better if each item can get one line of potential and only one line of potential. But it's too late for that.