I was actually asking what kind of move you would be using, I wasn't being sarcastic. If you'd give an example then we could go more into depth on usefulness. I never said I like invincible DPs by the way. In fact I like the way it is now where certain positions/angled attacks can hit/trade against a non-EX dp, where as an EX one which requires 1 power gauge is invincible.
Theory and generalization of moves is not the way to discuss things. Give an example and we can expand on it. I'll start it off with a couple:
I noticed K', as well as a few other characters, can j.CD and hit at the tip against a dp and trade/beat wake up DPs such as Andy, with the j.CD doing more damage (worth it, not punishable).
Against K', his dp+A can be beaten/trade by a lot of deep j.C's such as Robert, Kula. His dp+C will beat it, but has slightly longer start up. This means if someone does a really deep j.C against his dp+C, they will land on the ground and have time to block it. I believe Terry's d,u+P is similar.
Also I've noticed fireballs will beat some dp's and will go through others. You can verify this in some of the technical reference vids. And as I've said before each dp is different some have more/less invincibilty.