I have a hunter character with lvl60 thowing. I found a cow and a bull. I was able to kill the cow, so I went back for the bull. After kiting him to my claim, I spent 2.5 hours trying to kill him. I hit him with hundreds of arrows and rocks. It was suggested in Help that his HP regen was faster than the damage I was causing. I dont see how that is possible, but oh well.
It would be really great if the devs could provide players with some indication that their efforts are in vain. For example, if a player is attacking a creature which regens at a faster rate than damage taken, a simple, "You realize your efforts will be in vain with your chosen weapons and skill." could be shown. Code-wise, it would be a damage-over-time calculation against the hp regen-over-time the animal has.
A message like that would spare players many wasted hours of trying to do something that simply will not get done. My only consolation was gaining thousands of experience from the torturous ordeal. Frankly, I would have rather had the hide, meat, and bones - which was my intended goal.