Suggestion: make spilt blood persist for a while

That way there will be evidence that someone was there and was bleeding... and then you would know you weren't alone, or you could use it as a clue to track down a player or a mob that you hit.

After a while, the blood would of course fade.

The same thing could be done with footprints in certain environments and conditions (sandy, muddy, snowy).

Later on in development, a Tracking skill could always be added that would allow players with a high skill to pick up a greater % of these types of physical evidences, or be able to better figure out where they lead, such as with the Witcher sense in the Witcher games.