Although it may be a cloud device it is far from being complete. It is getting there slowly but it is more of a nas box then a cloud box.
Take the wd cloud back and refund it and get the following app. The app that you want is called air video in the apple App Store and the air video server software is needed to run on your Mac. This program will play any format file and convert on the fly all formats including mkv and stream it to your iPhone iPad.
Optionally you can do what I do is map the cloud as a drive and use air video to stream from the wd device as a network drive.
Thank you, I’m currently reviewing this app that you recommended. I’m also utilizing VLC on both iPad and iPhone. I’m going to test the VLC FTP server option to try and connect on a different network ex. friends, office etc.