Should I opt out for NTUC income DPS?

If you mean, can you claim it with other insurance policies, yes you can.

I opted out of DPS because we use OA to pay for it, and my OA is losing 3.5% interest on the monies used to pay the premiums.
I already have my private insurance policies in place so I feel I can save some money there and grow that premiums used instead.

Only consider this after you have adequate coverage in the event of death first. A good figure to have is either 10 X Annual Income or 25 X Annual Expenses as coverage paid out in the event of death, whichever higher.

Hi,
You should cancel your DPS as you are using your CPF OA to pay for it.
Why?

You are losing at least 2.5% interest on the CPF OA, that can be used for better things like your future house. You should take a Term Direct Purchase Insurance ("DPI") of the same Sum Assured to cover for the shortfall, since you going to cancel the DPS. Check here: http://www.comparefirst.sg/wap/searchProductsEv...
Why?

You will be using cash, which I assume is not earning you more then 2.5% returns. Anyway Term DPI are super cheap, assuming you are 20 year old male non-smoker, you are going to pay only $45 annually for $60K Sum Assured, instead of the increasing premiums like DPS ($36 to $260).