Azure TempDB and Log files
Azure IaaS is a different animal than traditional on-premise servers (virtual with a SAN or purely physical).  You will get at best 500 IOPS per drive attached.  

General recommendation is to use storage pools to stripe multiple drives to increase throughput.  

With only four drives available on a D series, I would do the following.


Put TempDB on the D:\, it's an SSD.  Don't put anything else there, make sure that a startup script will check that drive for any folders that are necessary and fix permissions if required.  
Stripe the four disks you have into a single driver and put both your data and log files on there.


If you had 8 disks available to attach then I would recommend doing two drives of four disks each and putting log on one and data on the other.