Not easy to explain really. Sometimes its hard sometimes its not, mostly depends on enemys movement speed and weapon speed. Duel between two man-at-arms can be very fast, but dueling with greatswords will make blocking must of the time easy. tbh aiming blocks is easiest part of the game. Not ridiculously easy but not that hard. The hardest part is distancing, timing, footwork, dodging. All this things are way way way harder then in warband, and all fights finish in 5 seconds , no matter how armor is heavy or shield is huge. The longest duel I saw was like 10 seconds. If you will be too passive, a proper feint will 100% get you, if you are too passive with shield, you will lose all youre stamina = death. Needles to say I didnt had so much fun in M&B for years, especialy in cRPG with endless boring block fights.
On top of that there's that stamina system, I'm not sure how it works entirely but it seems that if you're outnumbered you're pretty much fucked even though you might be superior in skill.
Well I won 1v4 situation in my first day of playing. You can hit and block several targets at once so not a big problem. Stamina punishes you for being too passive (especially with shield) and for spaming with kicks/shieldbash and combos. You wont lose stamina for making a single strike or sprinting.
