You need a LOT of stamina to bash. it takes too many hits for me to kill someone to be able to rely on that. Perhaps i should get my 1H up.
Actually, if you run out of stamina, just keep blocking until you do have enough stamina (keep in mind that blocking does take stamina as well). I put all points into stamina first, health second.
Better yet, when you run out of stamina, walk backyard and evade attacks.
Just try it:
1. Block
2. When they ready an attack, bash
3. Counter attack (normal attack and power attack while circling around them)
EDIT: Circling around them lets you easily evade their next attack, allowing you to regen stamina.