If you die often, you won't notice that stamina is drained way too much from sprinting alone. It prevents you from fighting multiple aliens in quick succession; you'll die from your inability to move, rather than your inability to dodge. This was never the case in 1.1, and it shouldn't be in 1.2, so I'm glad they're changing it.
About dretches: you need to learn better dretch tactics. I have had no problems dretching humans, regardless of sprinting/dodging. Charging humans is the best strategy for losing; using corners and hiding places, flanking, etc. are much better options, and they negate a human's ability to dodge away. Rifles had the advantage against dretches in 1.1, anyway. It was always easy to dodge them.
Also, humans won't become faster if they change stamina. They're changing stamina, not speed. Many dretch vs rifle fights probably begin with full stamina, so you might not even notice a difference, unless you're attacking in waves (and even then, you'll probably kill the human).
I don't think they're boosting stamina either; I think Norfenstein said he'll reduce sprinting's drain on stamina.