I have been re-enactor since 1996 and, sometimes, I have worn chain main ten hours per day in a filming of two weeks (the guy of the avatar is me). You obviously carry the weight of the hauberk with all the body, but the heaviest part of the gear is the shield, because you hold it just with an arm and the historical ones were heavier than the modern replicas. Actually, in the Antiquity the type of the warrior depended of the shield he carried (hoplite, peltasta, scutati, caetrati, etc) which determined if he was a heavy infantryman or a skirmisher. It wasn’t the lorica hamata the only difference between a principe and a velite.
The first time I tested the stamina in VC I had a similar impression than yours, but if you consider the circumstances of the game in a real context, sometimes you are forcing the character to charge 300 meters to the top of the hill with a full armor. In the megaHastings of 2006, I took part in the Norman left wing, we had to go up to the Abbey’s hill over and over again and I felt exhausted. I’m a kendo practitioner and I have trained with a bogu during two hours without stopping, and now I practice longsword in HEMA style, but even if you are well trained and you know how to breathe in the stress of a combat, your performance goes down after an important aerobic effort.
In Viking Conquest the stamina recovers each 3 seconds when the player is not attacking or running. I think this is realistic as, in an actual combat, the warriors probably fought in a conservative way and the shifts between lines existed during the whole battle. Therefore, I think this kind of stamina force the player to imitate the normal develop of a Medieval battle. Though this is just my opinion.