Rotherham manager Neil Warnock admitted a shocking 20-minute period in the first half, when Hull scored four times, was as badly as his players had performed since he joined the club.
The Millers went down 5-1 having opened the scoring through Lee Frecklington on 15 minutes.
Hull were level as Abel Hernandez nodded down a cross and Robert Snodgrass curled the ball into the top right corner with 25 minutes gone.
A minute later Hernandez scored with an overhead kick and Jake Livermore netted Hull's third six minutes before the break as he touched the ball past Lee Camp before scoring from a narrow angle.
Two minutes later Mo Diame scored Hull's fourth, beating Kirk Broadfoot to the ball before skipping past the defender and shooting home.
Hull extended their lead on the hour when Livermore scored following a clever backheel by Snodgrass.
Warnock said: "We started the game well but we had that 20-minute period where we just lost the plot.
"We were very lucky to get away with four. We had to play for our pride second half, I didn't want to get battered by eight or nine goals."
When asked what he said to his players at half-time Warnock responded: "I couldn't really repeat it to be honest but my blood pressure went up a bit.
"If you are as bad as that in certain areas you are going to get battered with sides as good as Hull are.
"They showed if they are not all together they can get beaten by anybody."