Ok, first, this game is about fun, so you don't have
to win. It's that kind of attitude that leads to powergaming and bad sportsmanship.
Anyway, I'll critique your list now
-Ok, first. Your Great Unclean One is going to be possessing one of your AC's. Which means that you'll lose one model with a Powerfist (and you've only got two). What I suggest if giving the other Plague Marine squad another AC and giving him Daemonic Chains. You only have to pay for D. Chains because the AC is free.
-The predator's ok, but it's the one that's going to get raped if you don't deploy it right.
-Give the AC's something else, like D. Mutation, to help them against the Ogryns.
-I also don't really like the Great Unclean One, but he could work...