Here's my take.
The ending is atrociously written, with neither the Catalyst, the problem, or the solution, grounded in the story. I do like that there's no winning scenario and that this is a choice among ideologies. I like the epilogues. I like the tone shift. I like that a certain class of player was angered. But the ending was still a mess.
What is this tone shift you are speaking of? Were you comparing the endings of each game of the trilogy? or were you talking about the ME3 ending in relation to the whole trilogy?
Either way I do not feel there is a massive change in tone, many choices throughout the games have dark overtones, and sometimes bad consequences ensue from "paragon" actions, albeit badly shown
Now, let us ignore all the moralities and philosophies for a moment and consider synthesis, can we really say it is an ending with a dark overtone? or with a tone that has shifted from the previous "happy" mass effect games? Where is this "loss" in synthesis? Also, in synthesis, it seems that EVERYBODY wins, not "no winning"
@Massively...and no, spamming the top left corner dialogue is NOT a right, but a privilege, you had to work hard, do many mindless quests, speak to and not kill people you dislike, being patient when the situation is deteriorating and be thoughtful of future consequences. Yes, BW is biased towards paragons but that doesn't mean they get a jail-free card for every decision they make