How high is the Collect chance?

[test95]

Hello,

I was thinking about the chance of receiving things after killing mobs.

Exist there known values about that?
E.g. How high is the chance of getting a normal/spezial/magical/epic/legendary Item?
I know, it's not high, but I want to know the value and Influences.

How [speciffic value] is the collect chance changed, if the level of the Mob and the player not equal?
How [speciffic value] ~ if there attacking two players one Mob?
How [speciffic value] ~ if players are in a party, and the Mob reduces its difficulty? [e.g. difficult to easy]