How are you supposed to know if it's so subtle?
Emet-Selch effectively worked against the interests of Zodiark in Shadowbringers, so if Hydaelyn's tempering is the same why would her champions not be able to? It seems to me that she needs to actively go out of her way to control somebody.Then you also have the Warriors of Darkness and Cylva who all had Blessings of Light and all joined the Ascians to fight against Hydaelyn, in addition to Saint Ajora who also had the Blessing and summoned an extremely evil entity to the planet that nuked a whole city and threatened to corrupt Hydaelyn herself.
The explanation she gives is "like the Ascians and Zodiark, some people need to serve me as well".People have brought up Minfilia stopping Ardbert before in these forums and that's a very weak argument for his being tempered when all that happens is that she stops him so she can explain herself to him and then he gives up. If he were tempered, then she wouldn't explain herself after.
The interplay between the Blessing and the Echo, especially that early in the game, it poorly expounded upon at best. Minfilia didn't have a crystal and wasn't a Warrior of Light - However, she was chosen as the Oracle of Light.As for Minfilia, she doesn't even have the Blessing of Light, so you can't really consider her actions to be a result of being tempered.
The question of WoL's relationship to Hydaelyn and potential tempering keeps being brought up, so I highly doubt this is an issue that is just going to be ignored or sidestepped in Endwalker.