It is alright. Since we are limited by todays technology of course it isn't going to be near 90% realistic.
I've seen some neat things with javelins and arrows. I wouldn't want to play without it now because it adds a certain something. It is a good idea to watch the replays even the ones taken before dlc just to fully take in the blood damage.
What is almost most important to me is that kill animations on the campaign map have blood and they do. I also like having blood on the main menu.