Would like to know some mechanic of the game   [4]

Bleeding decrease healing

Bleed is affected by AP stat and level of its skill (bleed is always caused by using skill). Damage by bleed has nothing to do with enemy HP (though it is affected by DP), so the same amount of damage to a 3000HP hunter will be done to a 2000HP hunter. Also, to expand on DerpScout's answer, bleed cuts healing by half.

Bleeds cannot crit, nor are they affected by the block mechanic. However, all sources of immunity will cancel out bleed to 0 (whether activated before or after bleed has started, does not matter), so that is one way of countering it. Otherwise, bleed damage per popup will always be constant.
As mentioned previously, bleed damage will be reduced by the defending hunter's DP, and is further affected by elemental weaknesses. I believe element has a 20%(?) impact on damage, so the bleed will have a 0.8/1.0/1.2 multiplier depending on whether the target is strong/same/weak against the attacking hunter's element, respectively.

That sums up my knowledge on bleeding, Hope this wall of text doesn't hurt too much :)