A stamina bar would allow you to combine short-term cooldowns for minor abilities (like, uh, Knockdown or relatively low-level spells that aren't very useful anymore, but can still help) with attrition. It basically solves the attrition vs fresh start every fight problem because it provides a limit to your cooldowns or the damage you can take. It'll lead to harder, more satisfying encounters if implemented right. You still have attrition: health. Ideally, in such a system, spells would start to cost health once you're out of stamina, or simply not function at all.
But there's a chance for the horror scenario if the numbers are tweaked the wrong, I can admit as much.