Regarding ore related "profeciency skills" mechanic details.

[YellowGhostoMain]

Skills that increase the % of success for ores smelted like Deep Artifice, a what point exactly is the skill applied, during the actual mining of the ore or is it tied to the construction of the smelter?

My worry is using an alt that doesnt have the skill smelt the ore and missing out the bonus success rate by doing something wrong and never realizing it because there's no way to know if its applied.

[Mashadar]

It's the skills of whoever mined the ore that matters for the smelting chance.
So it's safe to use an alt to smelt it.