there are ways to win archer v shield+sword even when he gets close
what you do is hold your arrow once he gets close, and as soon as he lowers his shield to attack you, release it. since you are standing point blank, you should hit even though your aiming reticule is huge from holding too long.
if you hit him, his attack will be interrupted and he will raise his shield again, allowing you to nock another arrow before his next attack and repeat the process
if you DO miss, then most likely you will die, but i find that sometimes if i run straight at the swordsman he will start backpeddling and sometimes eventually get out of range to strike you (or just forget to attack), giving you a moment to draw.