I think it starts going off the rails a little earlier than that but with that ending, I really have no desire to go back. I'm not the type to demand a different ending but if they do end up coming up with something that isn't universe destroying, I'd take a look.
Also, the indoctrination theory is possibly even worse than the ending taken at face value. How could you build up a 90+ hour trilogy and end it with the protagonist unconscious, dreaming without an ounce of closure? There is no way to salvage the ending; if they want to fix it, they would have to start from scratch.
Oh I agree - after the arrival of Harbinger everything turns to shit. But the complete nonsense started as soon as Space Jesus were lifted by the Space Elevator. If Bioware are looking into revising the ending, they need to remove that shit entirely. I can live with Illusive Man appearing out of nowhere or Anderson somehow arriving at the Citadel before Shepard, but I will not accept seeing Vent God appear again.
I especially do not ever want some fucking kid tell Shepard: "NO YOU CAN'T." when it concerns matters that affect the entire galaxy.
Or what Emceegamer and Y2Kev mentioned last thread:
"Catalyssssst, if you don't tell me show me your grades then I'm taking away your new Nintendo."
"NO! You CAN'T!"
"Can we just keep our own bodies?"
"No, you can't."
"Why not?"
"If you do, you will be harvested by synthetics."
"You mean like now?"
"That you are standing here is proof my solution no longer works."
"Why?"
"...I need a new solution."
"Why?"
"Please pick your favorite color."
"Can I please speak to the manager?"