Should n't b internal auditors report directly to entities outside organizations to enable them more independent. for e.g to regulators?

Yes, the law oblige sometimes the internal auditor to inform the industry regulators. Also in case that if he don't inform the appropriate external parties he will be liable of a crime... But the reason is not because the external parties are more independant. 

This is an exception to the general rule, the IA has to do it only if obliged.

Internal Auditirs get mandate from the promoters or top management of the company to carry out ceck work within the scope  stated in the mandate itself .

Internal Auditor  should report to AUDIT  BOARD  only and AB  must comprise of members from within the organisation and some senior experienced professional from outside  so as to make his position in the organisation indepedent and his report effective .

An external member may not full appreciate the typical problems faced by the organisation and top management may not like to share it;s weaknesses and secrets with an external . So the external member should be high integrity , rich in knowledge and experience plus less vocal .

No...Internal auditors are for rectifiying rules and procedures of accounting system to shw the clear picture of the organisation vide P & L account and Balance Sheet.