I have no links to patch notes or discussions backing up my observation, but it seems to me that characters lose stamina from movement much faster here than I have ever seen before. I played Ultima during T2A and quit just as Trammel began, so I wouldn't know if there was a change to this entering or during UO:R. But I never used a mount during a year of playing, for various reasons - a lot of players went on foot back then - and I can say with certainty that if stamina loss had been this fast, I would've broken down and bought horses. I'm stubborn but not a masochist Currently it is hell to travel any significant distance on foot running, and you also do not regain stamina while walking (you lose 1, gain it back, lose 1, so on to infinity).
Jump on a horse either no Stam loss or horses have a ton of stamina I've yet to run out. Maybe I need to travel farther on horse to test it.
I went out on foot to try and mine and died. Monsters target from quite a ways off screen, they cast magic immediately without player aggressing first, and they seem to track you forever. Add in the quick stamina loss and it's a recipe for noob disaster lol.
We will run some tests Zagyg and double check the passive stamina loss from movement, we actually have patched this already to reduce stamina loss from low level movement. However it could still be draining to quickly.