I want to talk about tempering

[Dualblade]

Ysayle is probably the biggest indicator that regardless of whether Hydaelyn's blessing counts as tempering we still have our free will because there is no way the Ascians would have been able to manipulate her into the whole Shiva deal if Hydaelyn had as much control over Ysayle as a normal primal has over their tempered. I'd also say the WoL having access to the DRK job is another one given we are using Hydaelyn's opposite element.

PLD WoL would be the most likely to be mind controllered temepered honestly.

As far as the Scion's aetherometer goes it should have already come up if it was able to tell if someone was tempered or not, more so since Y'shtola indicates that her own vision can do so. This also indicates that Y'shtola's new eyesight is better then the aetherometers but with the rather bad drawback of "My death will soon become plot relevent".