I think this steps on the toes of Improved and Superior stamina, since they both already increase a stamina bar. This would just be the objectively better purchase. What could work is if Improved Stamina had two branches (Superior Stamina/ Energetic Stamina), and instead of boosting the stamina bar you focused more on the active effect.
I do like the idea of having a temporary effect that's more noticeable than the "okay" speed boost of something like Divine Barrier.