DPMA is not health insurance nor is it an investment opportunity. I believe you only have a one-time chance to sign up for it and the window is limited. In short: get it.
If you were to be hit by a car tomorrow or get diagnosed with diabetes or whatever, Delta's Long Term Disability will pay 50% of your earnings. The DPMA benefit kicks in another 20% to bring you up to 70% of your monthly earnings, which is approximately what you take home after taxes. That's the whole point of DMPA....so that you and your family do not experience a financial hardship due to your inability to work.
Its a great thing considering approximately half of us will have a disqualifying medical condition before we retire from flying.
Its some of the cheapest insurance around and its very well administered.
Hope this sheds some light. They apparently didn't explain this too well in indoc, but there is a ton of info so I can see how you'd miss it.
Happy New Year!