What probably annoys me the most, aside from 343i flat-out lying to us, is how they've been giving us the false impression that the universe is moving on to an exciting new direction after the transitory episode that was Halo 4. Especially after we learned that Blue Team's going to accompany the Chief now. Killing off Cortana was a bold move, to be sure, but since they did it anyway they should've stood behind that decision instead of this horribly obvious backpedaling we're getting now. The story they said we'd be getting -- Chief back with his team, questioning things, coping with loss and growing as a character -- sounded like a great setup and a good way to open up the universe. Unfortunately, if even half the spoilers are true, this isn't that story. The very fact Cortana is alive in any shape or form ruins it all.
And let me be clear, I'm not even a Cortana hater. I liked her for what she was, which is why I'd have preferred that she stay dead because that would've been the respectful thing to do for both the character and the audience. But somewhere along the line the writers apparently got the idea that she isn't just a particularly clever software infiltrator, she's an über special Sue ex machina who's part of some grand genetic destiny. It's as if 343i was afraid to follow through with the idea of Cortana being dead just because she's an iconic character, and so she must continue to be massively important in the story too. Granted, it's a pretty common problem with fictional universes - characters' fame in the real world starts bleeding into the narrative until they've become bloated parodies of themselves.