They all do it. It's a characteristic of the Cummins engine. That's why it's called the Hummin Cummins. Some people are bothered by it and some aren't. That's why some perceive it as a bad vibration and others see it as a slight drone or barely noticable. Some trucks for whatever reason seem to amplify it more than others. Maybe a tweek in the exhaust or cab mounts a tiny bit one way or another.
If you lock out O/D with the auto or run in direct for the manual, you'll notice it at 2100rpm but it's not as pronounced. O/D must help amplify it with the different rpm of motor and driveshaft. ??? You can also rev the motor to 2600rpm in neutral and feel the same vibrations to a lesser degree.
If you're all torqued out of shape because your Cummins sounds and feels like a Cummins after spending $30-40K or more, you'd really be torqued out of shape if you'd have bought a $98k SuperCruiser or FL70 Freightliner only to have it sound and feel like a Cummins. My Harley cost as much as a nice car too. But it still sounds and feels like a Harley. Cummins and Harleys aren't known for smooth quiet operation.
I'm not making excuses for a truck that costs as much as a luxury car. But it's not a luxury car. It's a truck with a Cummins engine. That's what it sounds and feels like. Leather seats and power mirrors don't change that.