The dealer has tools to get the regen on.. since it would never work for you on the highway, and it sounds like it's not working for them it does sound like a new DPF is in order. I'm assuming your still under warranty?
If it's a great deal, and doesn't hurt you wallet I would do it just for the warranty. But that's just me!
But, I do see your point about not having any issues. It seems hit and miss..