I have make some test and find some bug:
I have set a Group for developers, and unmark View all prejects, but mark View Only Assigned Projects.
What i have found is that when the developer user access he can view all Task that has no assiged to anyone even that the project is assignet to some one else.
The idea is that i can hired developers and help me with projects but has no access to any other information about other proyect.
Thanks for reply to let me now i was clear.