That's a solid plan, but the plants need to be well-established first. Fresh plantings won't hold soil until their root systems grow in fully. It's a slower fix than rocks, but it works great long-term.
Used to think rocks were the only real answer for slope erosion until I tried it myself. @barnes.seth is totally right about giving plants time, my first batch washed out because I got impatient. The second season, once those roots dug in, everything locked into place better than any gravel bed I've built. Sometimes the slower way is just the permanent way.
Two whole seasons before it held? That's a long time to wait. I would have given up and used rocks again after the first washout. Your patience really shows how plants beat gravel in the end.