Disk Queue length of 30 in Azure App Service, that can't be right
To me, that sounds high as well, with Azure your in a shared pool environment. I bet your back-end disk is getting hammered by other clients. Based on other posts it sounds like Azure is known for this. I would see if they can relocate your backend disk to less used storage or try the recommendations in these posts or others.
Performance azure disks, high average queue length
Azure IO performance