I have completed the Severn River raids on every map site three times and the trousers have not spawned. The armor pieces should be limited to military camps, correct? I have tried Severn Outpost, Lower Camp, Island Camp, and the five Small Camps. The other two maps seem to have worked properly. I am playing on Xbox One. Thanks for any help you can provide.
Hello there!
I'm sorry to hear that you've been unable to find Saint George's trousers. Would you be able to send us the following information so we can take a closer look:
We can then pass these along for further investigation. Thanks! 
Hello there @d0nt_panick
Thank you for posting, sorry to hear that you've been unable to locate all pieces of the St. George set.
The items’ locations are random spawn inside some of the big chests in the large military establishments. There are two items available in each river raid (and an extra item after defeating the River Champion):
River Exe Raids -
River Severn Raids -
River Dee Raids -
If you're still encountering issues, could you please confirm for us if you're missing the trousers, or a different piece of this set?
Many thanks.
devtrackers.gg