The Atabapo I pikes would do fine if introduced at the same time as the other fish. Their aggression is more intra-specific and they aren't tough on other similar-sized fish. As long as they all have plenty of room, as in a 500 gallon tank, they will do fine. (I have an extra M/F pair of the Atabapo I's if you're interested.)
The discus might have stress issues with the aggression levels of the other fish, as well as trouble competing for sufficient foods. Discus prefer to graze off of the bottom, so the activities of the other fish might keep them moving too much to feed properly.
Otherwise, the combination of the predators sound good. I really like the tigrinus cat.
Why not keep a separate tank with the discus with the Tutti-Fruity tetras?
Mike Z.