We have been having an ongoing issue with address validation on shopify for the past month and a half and have been on the phone and email with shopify support and they have not fixed this bug. It mainly effects international orders (the middle east seems to be the trickiest to validate) but I've seen it happen with domestic orders too. I also have the shipping program endicia for USPS, and everything always validates fine on there. The only issue is many international customers want DHL because it's a more reliable and quick service. Shipping directly on DHL.com is cost prohibitive, and only worthwhile to do through shopfiy shipping due to the discount of their builk shipping account.
Is anyone else having this problem? Have you found any work arounds?
Shopify has acknowledged this is an issue but has told me there is no time table for fixing it. They said other shops are also being effected too.
Is the issue fixed?
Address validation is something that is automatically done when an order comes to the store. Now, if that is happening incorrectly, then you need to use a Shipping app that validates the address and helps you ship. However, as you mentioned, going with Shopify's carrier integration makes sense as rates are way cheaper than using your own account. However, if you have an account that has heavy discounted rates, then you can use the Multi Carrier Shipping label app that automatically validates addresses using your own carrier account.