The Tricaster 850 does lovely HD quality streaming to ScaleEngine's Video CDN, but its basic settings don't set the Profile correctly, so the video looks choppy and jerky. The Tricaster interface gives less control than is available in the xml. This also applies to the standard, earlier Tricasters. They are all using FMLE to stream to CDN.
Exit the Tricaster application, and in Windows Explorer navigate to your user folder and find the FMLE settings folder. There are several xml files there. Copy the one you've been using and name it after your project. Open the new xml file, and find the Profile tag. It will be set to "Main". Change it to "Baseline". Confirm also that you are sending a keyframe every two or three seconds. Save this file and reenter Tricaster. You will see your new profile. Stream to ScaleEngine using it, and view a smooth stream on the iOS device.
This page on iOS settings also has a great deal of useful information.