I just ran through the setup of the DJI go app for a new Phantom 4 on an iPad Mini. I was expecting perfect live video feed but with the transmission quality turned right down and trying both auto and custom channel selection the video feed is still broken, green strips and delayed refresh. I can not fly with this feed quality. The feed is perfect on an iPhone 6 and perfect on the SD card. Any suggestions on what might be causing the issues on the iPad only would be great.

A quick check on the recommended device list shows the iPad Mini 2 and above, so I would guess that your iPad Mini is not powerful enough to display the video properly.
The fact that it works fine on your iPhone 6 (on the recommended list) and records to the SD card fine, confirms this.

Hello ausflats, it is recommended to use the ipad mini 2 or later generation. What's more ,for IOS device, you can enable the Hardware Decoding in General Settings.