Donoghoe was hit with a grade-two charge for a careless high tackle on St George Illawarra prop Francis Molo in the Dolphins' disappointing 26-6 loss on Sunday.
The suspension adds to the side's dummy-half issues, with starting hooker Jeremy Marshall-King suffering an ankle injury against the Dragons.
Marshall-King was in a moon boot after the match and will go for scans on Tuesday, but Bennett said he was unlikely to play against South Sydney in the home round-19 clash after this week's bye.
It was Donoghoe's fourth offence this year, so because of his history he copped a three-match ban for a guilty plea, not one.
"He did what he did so he's got the consequences. I have no sympathy for that," Bennett told AAP.
"We still don't know what the prognosis is there (with Marshall-King), but we don't expect him to be right (to play the Rabbitohs)."
Bennett said versatile lock Max Plath would likely play hooker against the Rabbitohs.
He said his side had other issues than at hooker. The Dolphins led 6-2 at halftime against the Dragons but fell away.
"Our second halves have been a problem for the last five weeks when you look at our scoreboards, so the penny is dropping for us all there," Bennett said.
"They had 26 sets yesterday to our 13, and eight penalties to our three. We are not that good. We can't give (the opposition) that much."
The Dolphins have lost four of their past five games to slip from fourth to sixth and just one point ahead of ninth-placed Manly.
It is a slide they must reverse, starting with the clash in Redcliffe against a red-hot Rabbitohs outfit.
"We have put ourselves in this situation, with the good and bad of it," Bennett said.
"The bottom line is that we control all that and no one else can drag us out of it except ourselves.
"The injury toll is starting to get a bit high again, so that makes the challenge even bigger.
"Our first halves the last four or five games have been tremendous. We have either led or been right in the game. Yesterday we got in (at halftime) at 6-2 and self-destructed in the second half."
Bennett said prop Thomas Flegler was no closer to returning from a shoulder injury. The Dolphins won't have State of Origin players available for the Rabbitohs clash.
Fullback Hamiso Tabuai-Fidow (AC joint) missed the Dragons loss, but Bennett said he would be right to play for Queensland in the Origin decider.
Forward Felise Kaufusi played against the Dragons, but Bennett said he expected the veteran to retain his place in the Maroons squad and also be unavailable for the Dolphins.
