Some final bits of feedback for ODST (though these may be legacy problems you won't want to touch) -
In Firefight, Engineers probably need to spawn less frequently, at least on Crater Night. It's difficult to push out and go get the required Plasma Pistol or Needler if you get killed at any point while there are two or more Engineers out (or worse, one or more Engineers with Drones and the Black Eye skull.) Trying to deal with Engineers with anything but the two aforementioned weapons or a Sniper Rifle is an exercise in futility and frustration.
In Campaign: Friendly vehicle passenger AI is infuriating. When in a vehicle, AI tend to take very long pauses between shooting (longer than it takes a player to reload a given weapon), so you are often left vulnerable while driving. This is especially bad in the vehicular section of Coastal Highway, since Buck refuses to take a lot of easy shots even at closer ranges. It feels like there's a system at play that was trying to make sure "the friendly AI don't play the game for you" but instead it massively over-compensated and made it so "the friendly AI don't care about survival, yours or their own".