yes it is stiff to downshift into first ... luckily there is no reason to do so at the speeds it is rough at cause the brakes do a much better job of slowing the car down than the downshift and you won't need to be in 1st when you slow down due to the car having great torque throughout..

and you are absolutely right, it feels like you are going to break it when attempting to do so and i would say follow that gut instinct so you do not end up the unlucky few who have had to have their transmission replaced after it starts popping out of 1st all the time.

i've observed the same and test drove a few other xf's and it is the same in each one ... so all is working as it should and there is no remedy for it. still shifts nicely 1 - 6 and 6 - 2 ... going from 2 - 1 i just double clutch it to match the speeds and it goes in nicely without any force. giving the synrcos a little helping hand.