Stamina's unrealistic in 5-6 minutes skirmishes.
Fight for 2 minutes with all you have for your life, and let's see. And yes, even trained soldiers start to breath heavily after a few minutes of real fighting.
I think the stamina should be completely different from what people know from game like Skyrim for example. Actually I would make it so that without enough stamina you can still perform any action you want, but it will be weaker/slower than normal. As soon as you stopped performing stamina consuming actions your stamina goes up rapidly. For the whole bar to fill from 0 to 100% you need like 5 seconds. And let's say a blow which inflicted damage or got blocked costs 5% stamina, a blow which got stopped by you costs 10%. (It's because you need to waste energy to stop your blow again). That way you would already have that mass feinting lowered. Of course the value can get modified by weapon weight and length. Running takes about 2% per second (for horses too). Again this is modified by item weight.
The less stamina you (or your horse) have, the slower you (or it) will run. Your hits will deal less damage if you approach the bottom of the stamina bar, and your swings will be slower. Blocking a few times will give you time to recover.
I would like to see a reason to make "light equipment" viable again.