@Videoguy I just switched Rio Rachio so I'm just figuring this stuff out myself, and am interested in vegetable garden setups as well.
By drip pipe, do you mean the 1/4in tubing that had emitters every a inches, or the soaker style that is porous? I have a soaker house in our garden and have yet to measure the output. I guessed/estimated a 0.4in/hr, and am going to try to measure it this weekend. With those numbers, here in Arizona, it's been watering every other day this week at 55 min. but is predicting to go daily strain on Monday. After a watering today I checked the soil and it seemed reasonably most down to a reasonable depth, but I'm keeping my eye on it. Have you checked to see the moisture in your soil after a watering?
You might want to look at the effect of changing your vegetation type, which leads to a change in crop coefficient. I set mine to annual, which has a crop coefficient of 0.8. Shrubs have a crop coefficient of 0.8, which will lead to less frequent watering. I'm also using a root depth of 4". I'm not sure if that's entirely correct.
Let me know what you find as it will help me to get dialed in as well. Good luck!