Read: More coverage on the DOL fiduciary rule

"Access and affordability must be maintained and the final rule does little to help American annuity savers," she added.

The final rule sequesters fixed annuities from fixed indexed annuities, which are subject to new Best Interest Contract Exemption requirements, as are variable annuities.

That benefits fixed annuities, but by treating fixed indexed annuities as variable products, the final rule conflicts with a previous court ruling, which said FIAs are not akin to variable annuities or securities, according to Americans for Annuity Protection.

Now, advisors who recommend FIAs and receive compensation from insurance companies will be required to sign the BIC exemption with clients. Doing so will, of course, expose those recommendations to private action lawsuits, creating a boon for lawyers, potential new costs for consumers, and increased liability for insurers, says O'Brien.

"We had hoped for so much more from the Department in terms of understanding the insurance nature of annuities and the harmful impact to retirement savers under this rule," said O'Brien.

She also noted concern for the preference she said the rule gives to large ERISA 401(k) plans. Advisors to plans with more than $50 million in assets will not be beholden to the BIC exemptions, giving them an unfair advantage over IRA advisors, "at the expense of the private insurance market," says O'Brien.

That has the potential to discourage IRA rollovers, which can more readily accommodate annuity products relative to most 401(k) plans.

In spite of improvements to the proposed rule, O'Brien said "the devastation to the IRA annuity marketplace is still a clear and present danger to the very consumers it (the rule) has declared to help."

For annuity advocates, litigation may be the way forward. Americans for Annuity Protection will support those efforts, said O'Brien, who noted in a statement that DOL did not produce a cost benefit analysis the rule would have on fixed indexed annuities, and only did a "cursory" review of the impact on variable annuities.

Moreover, the $17 billion in losses investors suffer annually to conflicted advice, a number produced by the White House's Council of Economic Advisors and often cited as justification for the rule, was arrived at by "selective and inconclusive analysis," said O'Brien.

In a separate statement, Jim Poolman, executive director of the Indexed Annuity Leadership Council, which represents a consortium of fixed indexed annuity underwriters, expressed his group's dissatisfaction for DOL's decision to lump indexed annuities with variable annuities.

"It appears that this rule discriminates among similar insurance products without any rational basis," said Poolman in a statement.

"As a result, it will harm millions of Americans who need the lifetime guaranteed income that these annuities offer, and it will impose significant financial burdens on thousands of small businesspersons who offer sound financial advice to working Americans," he added.