We have this problem,whenever a workitem does not determine a agent, it send the workitem to everyone. 
This is causing lot of problems. 

This is generally a two part issue: 

1. At design time, you have defined the task as a 'general task' under the agent assignment. 
2. At runtime, when the agent determination routine tries to identify the agent, it cannot. So, because it is a general task, the task is sent to everyone. 

To resolve: 
1. Instead of making it a general task, try to identify an actual list of 'possible' agents. This could be by positions, userIDs, Org Units, etc. Make this list your possible agents instead of defining it as a general task. 

or 

2. Make sure your logic for determining the agent always return an agent. If you are using a custom rule, then at the end of the logic check to see if an agent was determined and if not, identify a default agent (like a WF admin or business analyst) that can receive the item and investigate who to properly route it to. 

FYI... if you go with option 1 and at runtime the logic fails to determine an agent, then an error message is sent to the WF admin instead of the task being sent to everyone. 

Which Agent did execute the task in the Inbox?

Which FW system field does contain the agent, whom has executed a task in her inbox ? 
If one of the agents executes task number 1 in her inbox, which system field do I have to use in task number 2 to find which agents did the thing ? 

Make a workflow container for Actual Agent of type WFSYST-ACT_AGENT 

and then in task 1 do the binding from task container to workflow container for actual agent. 

This container then you can use in your next task to see who was the previous agent 

Fast Links:
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