Efforts to get compensation for the US opioid crisis with two multimillion-dollar drug manufacturer payouts have been met by leading activists and addiction experts with a range of responses from incredulity to cautious optimism.

On Tuesday, the wealthy Sackler family and their embattled drugmaker, Purdue Pharma, makers of two opioids that triggered the crisis, Oxycontin and MSContin, reportedly backed a proposal to resolve all opioid lawsuits against themselves and the company for more than $11bn.

The potential settlement, if agreed by attorneys general across the US, would be the largest to date in the complex litigation over addictive painkillers, which have caused the deaths of about 400,000 people since 1999.

The proposal, first reported by NBC, came a day after a judge in a different case in Oklahoma found that drug firm Johnson & Johnson created a “temporary” public nuisance by tricking doctors into overprescribing its opioid-based medications.

Judge Thad Balkman ordered the company to pay $572m to Oklahoma as reimbursement for costs it incurred dealing with the surge in addiction and overdoses.

Shares in the company rose more than 5.4%, reflecting investors relief that the payout was far less than the $17.5bn the state sought and likely to bring down the liabilities facing drug companies and distributors that by some estimates could reach $100bn.

But the two potential payouts – one a pre-trial settlement and the other a court judgment – have brought widely different reactions.

Nan Goldin, the photographer whose Pain campaign has triggered widespread protests at Sackler-supported art institutions and forced the family to abandon philanthropic donations, told the Guardian the reported Purdue settlement would be “highly questionable” and that the Sacklers would still walk away as billionaires and experience no judicial judgment.

“The whole thing is orchestrated by the Sacklers and very well done, but underneath it’s highly questionable. We want them to be held personally accountable, and that’s not going to be possible with this settlement. They’re not putting their own money and threatening to go bankrupt. I think it’s blackmail,” she said.

Under the proposal, Purdue will file for bankruptcy, hand itself over to a trust controlled by the states, cities, and counties in the lawsuits, and sell its overseas drugmaker Mundipharma.

But the settlement only requires the Sacklers to hand over $3bn in cash. When last valued by the Bloomberg Billionaires Index, the family was worth $13bn.

The deal contains no provision for addiction treatment centers, pain-abatement alternatives, and the anti-addiction drugs that Purdue is offering are often not covered by insurance plans, although many addicts might not have insurance.

“This is great PR for the Sacklers – almost like their philanthropy – but they are not taking responsibility and they are remaining outside the law,” Goldin said.

Opponents of the deal argue that at least half of the sum is in the form of free drugs, including Oxycontin and its branded buprenophine Butrans, which Purdue manufactures at cost but will value at retail prices, so essentially profiting from the arrangement to distribute.

The proposed Purdue settlement could result in only small amounts of money reaching individual cities and municipalities affected by opioid addiction and depends on a critical mass of state attorneys general accepting it.

However, the Johnson & Johnson court judgment in Oklahoma can potentially be duplicated from state to state. It also reflects that the addiction epidemic was caused by a change in medical practice – that is, the over-prescription of opioid painkillers driven by deceptive marketing campaigns disguised as education.

“This is a landmark decision,” said Andrew Kolodny, a doctor and opioid researcher who was a key witness for Oklahoma in the case. “It would be nice of there was more money, but $572m will go a long way in helping Oklahoma address the crisis.”

The Oklahoma case, Kolodny says, recognized that the over-prescription of opioids contributed to a massive loss of life. Part of the benefit of the Oklahoma judgement, he says, is like the big tobacco settlement in the 1990s because the publicity surrounding the decision raises public awareness about the dangers of opioid painkillers.

But Oklahoma authorities will be watching closely how the J&J money is divided. A prior $270m deal between Oklahoma and Purdue in March resulted in almost $200m going to fund a new addiction treatment and research center. But Oklahoma’s 670 cities and counties, which absorbed most of the costs relating to the epidemic, received just $12.5m.

About $60m went to private attorneys, while the state itself got nothing.

Still, says Kolodny, the Oklahoma decision should still be celebrated “as the first time a court has ruled that opioid manufacturers are responsible for an epidemic of addiction and overdose deaths”.