I can understand where you are coming from- though I think you might be blurring the lines between conventional deadlifts and other forms which benefit much more than just your back. (rack pulls, sumo deadlifts, trap bar deadlifts)

Deadlifts as the exercise it purely is, is less likely to give you the strength for running you desire. Having been in the atmosphere of "Train as efficiently as possible", I can attest that deadlifts are far from a great choice for physical health. My 75 y/o coach would tear me a new one if he saw me wasting time training them.

I'm not surprised deadlifts have helped you gain a strong back, but having also trained for a marathon I can tell you there is a plethora of other benefits you will miss out on by training your lower back instead of your legs and overall cardio fitness.

>Deadlifts are great for running.

Leg blasters are significantly better and have a lower risk of injury.

Anecdotally, I have noticed that leg blasters (shitter squats in local slang) end up detrimentally affecting my balance. I never had this issue with deadlifts.