Im new to this - do they mean dumping a WU if it takes to long?  Block servers?

Dumping WU's: manually deleting a WU that is either stuck, doesnt download, upload or simply causes issues with the system. 

Blocking the address of servers known to "give less PPD" in order to only get WU's from servers issuing higher PPD WU's to boost your total PPD

Now that I completely understand context I think it draws the perfect picture @yaboistar