Employers are trying everything, according the Aon survey, "including subsidizing premiums at a higher level than other plan options (36 percent), covering preventive medications before the deductible (34 percent) and contributing employer funds to the HSA (30 percent) and HRA (22 percent)."

And a growing number of employers are finally listening to their brokers when it comes to supplementing these plans designs with voluntary products. Yet enrollment still lags.

"Employees want to choose the most cost-effective plan with the least hassle, but they often have very full lives and are not all that interested in digging into the details of CDHPs, HSAs and HRAs," said Joann Hall Swenson, partner and health engagement best practice leader at Aon Hewitt in a statement. "Our research and experience tells us that simply giving employees lots of educational information about these plans and accounts is only helpful to the small minority of people who like all the details."

Swenson's advice to employers?

"Get the right people into the right plan. Employers need to identify segments of their population most likely to value and take advantage of the unique features of the CDHP, and tailor the marketing campaign to them. Also, they need to monitor employees' day-to-day experience of using the plan to ensure it 're-sells' itself and engages consumers in the appropriate health and financial behaviors.

Reinforce the plan's advantages and actions. Employers should articulate what's in it for consumers, specifically how they can benefit from the plan's key features, and be very specific about the actions consumers need to take.

Make it easy for employees and their families to use the plan. This includes removing barriers to care at the point of need through initiatives like value-based plan designs or fully funding employer contributions to HSA/HRA accounts at the beginning of the year."