With the right system it wouldnt simplify things but just make it all more realistic.
I wouldnt call Assasin's Creed's fighting system that simple, It does have some numbers since you can purchase weapons and armor to improve damage and armor points, but its quite limited. You dont need it to finish the game, it just helps you a bit. The armor extends your life so that is somewhat usefull, but it can be broken and needs to be repared occasionly to prevent that.
The fighting is quite realistic in how the swords clash and how the duelists move, there are spectacular counter attacks, stepping away, you can disarm or pick up weapons of enemies to use them, grab enemies and throw them away or slit their throat, finish off enemies on the floor, and quite some other things.
To me this is real melee combat as it should be, there is still some room for improvement of course, but it definatly raised the standard, as Bioware keeps raising the standard for the story part of the game.
I am of course not saying they should copy the system of Assasin's Creed, I merely gave an example of what I consider to be the best system.