If you read the sales pitch for the Trek Domane you will understand why speed wobble is more likely with the Domane then most other road bikes.

It's the IsoSpeed technology that gives it that smooth ride. It allows the frame to "move with the road". We know a stiff frame reduces the likelihood of speed wobble, And limits the amplitude as well, Sometimes enough to allow us to keep control. But too stiff makes for a jarring ride.

It might be prudent to limit your speed to 50 kph down hill. Perhaps have a 2'nd bike when you feel speedy.