I quite liked the ending, except for one thing: the anticlimatic fight against Corypheus and his Dragon. (Sending him into the fade by opening a rift on him was just silly. All it needed was a Bond one-liner. I'd like to nominate, "Hey Corypheus, Inquisit this!" But I guess it is a good way of ensuring that the Inquisitor has no way of verifying whether Morrigan was right when she told him that killing his Dragon would make him vulnerable to being perma-killed.)
But about that final fight... If you are going to end your game with a boss battle in the first place, make the battle challenging, so long as it is really easy on the lowest difficulty setting; that way, if it is too challenging for a player at the difficulty setting he has chosen, he can always lower the difficulty.
Don't, for the love of God, do what Bioware did in DA:I - a multi-stage boss battle that any group with good equipment will breeze through on the higher difficulty settings, possibly even without using any consumables except health potions.
It feels dreadfully anticlimatic when the age-old Magister, who commands a dragon, whose power you all fear, and who has just used his mighty arcane power to raise islands into the air, deals negligible amounts of damage and doesn't have any defenses of note, just a rapidly vanishing healthbar and a few lines of dialogue every few seconds as you trigger his next retreat.
I am not insisting that CRPGs should have challenging final fights in general, but if you are going to have final fights against a Big Bad in the first place, and have gone to lengths to explain how he is personally extremely dangerous - you damn well better make him dangerous.
Jon Irenicus, Melisan, the Twisted Rune, or (perhaps better yet), the boosted Demogorgon fight, all from Bioware's infancy, are good examples of how to make memorable fights.