I agree, I dip everything I get now after I found some zoanthid eating nudibranches on a colony of new zoas.
I also suggest adding flat worm exit to your dip...you are already doing it, so why not be sure nothing is on there, including those damned flat worms.
Make sure the ro/di water you are using to dip is at the same temp as your tank, which I manage by putting some ro/di water in a plastic bottle, then floating the plastic bottle in the tank to get the ro/di water ton the same temp as the tank water that you are acclimatizing the coral to.
HTH
Stewart