Doing coop or solo with follower, even the follower tank, after i start shooting, mobs all will turn away from my follower or other players and start swamp on me. How to prevent that and what is the reason they ignore fighter and go after shooter ? They pick the weakest player(lowest defense) or the 1 do the most damage ? or its just my luck ? have to keep jumping around like monkey.

hey, u sure aggro system do exist in D3? 

i thought mobs always try to hit whoever thats nearest, randomly?