Dale hope to be in promotion contention themselves but, in stormy conditiions at Glanford Park, were blown away by three second-half goals.
Midfielder David Syers opened the scoring in the 57th minute with his second goal in successive games, before leading marksman Sam Winnall added a brace in three minutes to take his own tally for the season to 13.
"Scunthorpe are a very, very good side," ackowledged Rochdale boss Hill.
"They are the most effective side we have played against this season and I would not be surprised now to see them run away with this league, perhaps with Chesterfield.
"They have some very experienced players who will know how to play against teams in this division who are not as street-wise."
Hill was disappointed with the result - and with a red card in the second half for a second bookable offence for his full-back Michael Rose.
"There was not much in the challenge that earned him a second yellow," said Hill.
"Maybe, just maybe, the referee thought he had got it wrong a few minutes earlier when he let Scott Hogan off with just a yellow card.
"I thought a good League Two encounter was turned into a bit of a debacle at times.
"There was a spell in the second half when every time there was a challenge there was a booking.
"To be honest I was pleased to get away at the end with still 10 players on the field.
"I feel sorry for Michael Rose because he will now miss our FA Cup tie against Leeds on Saturday.
"It's a big game we are all looking forward to and we will make sure we go into that game with no hangover left from this."