I got them both. It just takes some strategy. I believe that if one is destroyed, the other will warp out. The trick is to have your anti-subsystem strikers disable them both early on.
An alternate method- and a pretty pragmatic one- would be to disable the Demon, hit C-3-7, and get a safe distance away, then sit back while the Demon kills the Typhon. In other words, let the enemy do the work for you. Then move in and finish the Demon off.