Hehe, medieval weapons and armor research in a nutshell. So many confusing, inaccurate names, many things that only have foreign names (faussard, zweihander, etc), and many things of which we still cant realy tell how they were used, and how effective they were to that end. Not to mention that fact that 'medieval' is used to discribe a period of 4 centuries, during which quite a few things changed. Popular media and inaccurate, out-of-context research doesnt help either.
Which is probabaly what has you confused here. Some folks took modern chainmail, went at it with some 12th century slashing swords and broadhead arrows, then a few indirect references later chainmail is invulnerably to 'all conventional medieval weapons'. Automata probabaly got it right with the main difference being that medieval chainmail did not have sophisticated methods of sealing the rings, they only had rivets and/or forge welds.
Plenty stories exist of knights being stabbed/shot through chainmail, chainmail-protected joints in plate armor were easy targets for daggers, and eventualy chainmail was replaced/suplemented with other armor wherever possible.
Yeah, closest thing to being invulnerable is full plate armor, and those have plenty of gaps and weak spaces ( not to mention being very late medieval development ), it is pretty invulnerable to slashing weapons for most part. Not so much against hammer-like or heavy weapons or piercing weapons like war picks, but it manages somewhat. Better than full suit of chainmaille, but chains are still a lot easier to manfacture with technology of the time and does the job for most part.
Powerful crossbows and well-trained bowmen could pierce the plate itself with right arrow and short enough range, though it'd be more toward longbow end for bows, but it'd fit right in with how DF stimulates things and how 'short' the normal DF range is, too. It's just a lot harder than against chainmaille
Way I see it, DF's more realistic than most thinks when it comes to ranged weapons, it just really sucks in adventure mode to get one-shotted so easily. Also reloading's way too fast, but that's more side effect of simplified weapon system. I don't mind seeing others rebalance it to be more fair, since, well, it is a game that can be tweaked
Though this' all off-topic and DF's pretty primitive stimulation as of present with such material, it'd take a lot of tweaking and testing to make it work together well, what's there works well enough for fun gaming. Also I'm not a medieval research specialist, I just read a lot and took a look at war records of the time, so take what I says with a grain of salt. Plus it's just limited comparsion between plate and chain, there're a LOT of different armors during the era, as well as weapons, or even variance within general types of armor and material used to make them.
