I love the concept, but personally don't care for how the statistics work out for rules-as-written. I would make the following modifications at my table:
- Disadvantage: if the character is hindered by injury or circumstances, role 2d4 and take the lowest.
- There are three possible outcomes: 4 = Success, 3 = Mixed Success, 2 or 1 = Failure. (You could grant "critical success" for rolling more than one 4).
The consequences of these changes are shown here: https://anydice.com/program/27ee5