When an item is submitted to workflow, it should be automatically validated. If the validation fails, the submittal should be terminated. If the validation generates a warning, the user should be prompted whether to continue with the submittal.
We've had several instances where an unbalanced or flawed journal has been submitted and approved only to fail when it is posted. There is also a know bug that will double book a journal. We've had this happen twice and it seems to be related to workflow items. Validation prior to submittal would potential reduce this risk.