I was the same when I drove a manual, in fact I used to be able to drive my 2007 1.4 TSi Jetta (the one which had twin chargers) at 30mph in 6th gear.I very seldom have my engine over 2000rpm, the economy goes down hill very quickly 🤷♂️
But the DSG box in the T-Roc has a mind of it's own and often refuses to change up until the revs get above 2000 and sometimes up to 3000. If I 'manually' shift up below 2000, the DSG will often just shift back down again. Arghhh ! (See this other topic started by Twist ... DSG getting “stuck” in 2nd )
I think my previous 1.4 TSI Golf DSG was better in this respect.
As for Sagwal's post, I can't offer any explanation, even for my own vibration. However it does seem to be a different issue if there is no vibration at lower revs. In my case, there is vibration at three specific revs which are multiples (1x, 2x and 3x) of the base which is around 1100 - 1200, although I don't normally rev the engine to 3300 - 3600