It really depends on the sea conditions. If it is rough, you will feel motion on every deck. We've stayed on deck 8 on all 5 of our
DCL cruises and the only time we felt a lot of motion was when we encountered 20 - 30 foot seas. On the EB repo in 2005, we went through part of Hurricane Hilary and had 30 foot seas. We had to take our DS to the medical clinic, which is on deck 1, and the motion was just as bad down there as it was on deck 8.