Try Azure AD Premium now! Microsoft released a trial periode for Azure AD Premium, and it is available from Your Microsoft Azure Portal.
Sign-In to Your Microsoft Azure Portal and browse to Your Azure Active Directory. SmartHostLink.
It is not available for Office 365 Syndication Customers.
Password Write-back for customers With DirSync and Password Sync activated, will be an Azure AD Premium feature when the new DirSync Version goes out of preview.