In fact, 83.2 percent of defined contribution plan sponsors took steps within the past 12 months to ensure compliance, with 61.4 percent personally reviewing the situation.

Many sponsors actually engaged third parties to review 404(c) compliance; 40.6 percent sought that review from their attorneys, while 42.6 percent turned to consultants. And the number of respondents who didn't know what steps had been taken to ensure their plan's compliance fell to just 7 percent, from 12 percent in 2014.

Most plans, the report said, are designed to be in compliance with ERISA section 404(c), at 81.3 percent. That's up a bit from 2014's 77.9 percent.

And although 457 plans aren't covered by ERISA, 18.2 percent of 457 respondents are 404(c) compliant—they seek to adhere to the standards even though it's not a requirement.

Plan sponsors are also looking at investment policy statements. Most DC plans (90.1 percent) have one, up from 84.7 percent in 2014. The percentage of respondents who don't know whether their plan has an IPS has fallen, from 2014's 4.2 percent to just 2.8 percent.

Those sponsors who are aware of the existence of their plan's IPS are looking more closely at it, too, with 84 percent of plan sponsors saying they've reviewed it in the last year. And of that group, 63 percent have made updates to the IPS in the past year.

Among other findings, 61 percent of sponsors say their plans have auto-enrollment, while four out of five of those plans with auto-enrollment also have auto-escalation.

Twenty-two percent of sponsors have evaluated the suitability of their plan's glide path in 2015, while 30 percent plan to do so this year.

And 97 percent use a qualified default investment alternative as the default investment fund, with target-date funds the most popular default choice at 86 percent.

The number of plans using their recordkeeper's proprietary target-date fund, however, has fallen from 70 percent in 2011 to just 32 percent in 2015.