The judge said the trial had taken a toll on the victims as they were each "called a liar" and efforts were made to "find chinks in their armour", as part of King's defence.
He said it was "extraordinary" to read a probation report that King maintained one of his victims was consenting to his sexual advances.
"It is an outrageous thing to say in the context of this case ... you put them through the wringer [during the trial]."
Last month, a jury found King guilty of eight charges relating to the indecent and sexual assault of four woman, aged between 15 and 57, in the back of his ambulance between January 2010 and June 2013.
All the offences in the ambulance took place in Central Hawke's Bay.
Judge Rea applauded the courage of the victims who came forward to the authorities, but said he had no doubt King's crimes will have "devastated" their lives.
He also spoke about King's actions on the St John ambulance service and found it "somewhat unusual" to read character references describing the occasions King had performed his duty professionally.
"We are not here about the occasions where you have done your job well ... the impact on those who work at St John has been significant.
"The ambulance officers who gave evidence during your trial must be in disbelief now knowing your offending took place while they were driving the ambulance."
Earlier this month, King also pleaded guilty to five counts of sexual assault against two girls aged 16 and younger between 2002 and 2006 in Napier.
Judge Rea was also unmoved by character references, including from King's wife, stating the jury had got it wrong.
"The jury did not get it wrong. I note none of the character references are dated after you pleaded guilty."
Each of the women assaulted in the ambulance were needing medical assistance. They included a teenager who had been beaten by her boyfriend; a woman suffering depression and threatening to harm herself; a young woman with a terminal illness; and a woman who suffered from temporary paralysis.
Prior to the sentence being passed this morning, the mother of the terminally ill victim, who passed away in February this year, said King abused her daughter's trust and "took advantage of her vulnerability and weakness".
"My daughter was very sick -- you caused huge heartache and emotional pain to our family."
She said a "sense of dread" washed over the family every time her daughter required an ambulance.
"We dreaded seeing you or bumping into you in our small community."
She said King's "lovely" wife and children have also suffered and were "victims as we are".
She also said King failed to have the "decency to plead guilty", forcing her family to endure the trial and publicity in the press.
