Conner doesn't fight Templar knights or Venetian armored brutes. He fights men who have no armor, and only some giant Scottish Highlander is able to survive a more than a few stabs. I suggest getting stabbed by a dagger or hit with a steel tomahawk with nothing but a few layers of cloth and see how you fare.
since when are games that realistic?
you know what a bullet does to your head? in 99% of the games it doesn't work like in the real world. ;)
You also forgot about the captains. Those guys are pretty heavily armored.
3 or 4 different guys. but when youve found out what to do against them. they all are easy.