Taleroth: Just press the letters. Right click/left click are irrelevant...
chhamlin3: tried this several times with no luck. I use the proper letters, but still get whooped
When the QTE comes up you should just press the button and release. Don't hold the button or tap it multiple times.
Also, forget trying to read the button letters. They always come up in the same layout as on the keyboard (W is high center, S is low center, A is left, D is right), so just react to where the QTE comes up on the screen. It's probably best not to even watch the fight, but simply stay focused on the center of the screen and react to the QTE's. With (very) little practice, you should be able to win fights without taking a single hit.