If your disk queues are that high you may need to look into adding additional disks to the server.
You will also want to look at your indexing on your databases. If you don’t have the tables indexes correctly this will cause the disks to work harder than they need to.
He is right, what kind of drive configuration do you have? Your ldf files and tempdb files should be on different arrays. If this is just one drive array and you can’t add to it your only hope will be to add more memory, but as your DB grows the drive will always be a bottleneck