I know this has been talked about before, but the last discussion I found was from 2.2.
Basically, I don't trust Hydaelyn anymore. Of course I have a deep seated distrust of authority in general, but in Hydaelyn's case it seems awfully justified. We can't be tempered, which seems to be something unique to primals. She takes crystals for power, and she grows in strength through prayer. ARR's ending showed us that people DO pray to her. Furthermore if the "Warrior of light" could be seen as a proxy for Hydaelyn, so praying to them, or having faith they will succeed, is the same for praying to "Hydaelyn".
Next you have the effect of what happens when Hydaelyn WINS. In Heavenward we meet the "Warriors of Darkness" which actually were the WoL from another 'star' (universe/dimension?). In their world they beat the bad guys and all the primals, which if any stated primal would do would lead to the end of the world. Which, surprise, is exactly what is happening to a world where the light wins.
Finally there is the echo itself. The gift of the echo seem to be able to take stress that would break normal people. Non-stop combat and saving the world? Well if our character shows any signs of straining...I haven't seen it. Even when someone was put through an insidious 'experiment', she seems to bounce back relatively quickly. But someone granted an echo through artificial means? She is on the verge of breaking down already. So something besides the echo itself must be getting imparted, something that wouldn't LET someone with an echo break. Something like...being tempered.
So basically, I feel there is significant cause for concern that the force we have been working for may in fact be the very thing we are working against. Or at least it needs to have some more screen time to explain exactly why Hydaelyn is any different from the primals or 'gods' that we have been going around slaying since day one of the game.