Just got our Inspire 1 with 2 Controllers. Seems the Slave controller loses video super fast and super laggy while master is smooth and has range. We are both running iPad Mini 2 updates, nothing in background. Our work around for now was running HDMI out of the master and into a monitor which was smooth.

Yep, slave video feed is a problem.
It worked just fine earlier on, but DJI made a change in firmware that cut the number of channels and transmit power.
Seems like they were originally using frequencies that they didn't have rights to.

Set your bit rate down as far as it will go and manually select the channel with the lowest noise level. That helps for some people.

Yeah we've played with those settings as well.  Hopefully they'll fix it in an update at SOME point lol.