 the last minute!?
Oh, sure, the game does MENTION them occasionally from early on. Meredith's name and policies do come up in conversation enough for the player to have a grasp of what her schtick is, and Orsino is, well, barely mentioned in any significant capacity, but not totally unknown. But hearing some rudimentary information second-hand about a character is not an adequate way of familiarizing a player with a character so fundamentally important to the game's ultimate conflict. Meredith and Orsino should have shown up earlier in the game, had their significance to Dragon Age 2's events SHOWN, not whispered, and in that process, there should have been far more interaction between them and Hawke, because as of this finale, the player has very little personal understanding of these 2, no real connection with them and scanty knowledge of their backgrounds, personalities, and motivations. It's just...it's like only finding out what candidates are running for president 10 minutes before you have to vote for one. The most you can glean from what little time you have to familiarize yourself with them is elementary at best.
So yeah, anyways, we finally get to the final battle. You have a moment to prepare, whichever side you choose, during which you can have Hawke talk to his/her party members one last time for some of those finale-speeches that party members always do in RPGs. These aren't really anything particularly special, certainly nothing as moving or epic as the ones in Dragon Age 1 were, but I don't really know how that could be improved--such speeches work well at the end of a long journey, and don't apply as well to an unexpected situation such as this one--so I can't really count that against the game. Then the fight starts.
Here's the next part of the finale that is stupid!  If you sided with the Mages, he'll be so overwhelmed by the battle's cost in lives that he'll go to extreme measures, and have to be put down by Hawke and company. This can be dumb in and of itself, since it's quite possible to have Hawke mount such a very strong defense against the enemy Templars that you don't see any Mage casualties actually happen, and either way it's questionable, as Orsino will lose it pretty quickly. I mean, it'll be like 5 minutes of fighting a handful of Templars, then Orsino will panic. If you sided with the Templars, the situation is slightly less stupid, as Orsino would actually have a good reason to lose his cool with Hawke and company carving their way to him.
However, the real problem with this scene is that it happens at all. What I mean is, Orsino is resorting to extremely forbidden, ethically intolerable magics. Apparently he knew this serial killer mage from earlier in the game, and uses his abominable research to combine himself with a crapload of dead bodies to make a hideous, uncontrollable freak. Now, what little we've seen of Orsino in this game just doesn't add up with this. The guy criticizes Meredith repeatedly for her being completely paranoid, for her seeing forbidden, dangerous magic everywhere she looks. He stands for the idea that Mages are not inherently dangerous or prone to corruption. And now out of NOWHERE he announces that he's well-versed in some of the most heinous, irresponsibly dangerous magic seen in the series so far, and then immediately employs it.
Even if you can argue that it's not completely unbelievable to his character that he would be involved with unholy patchwork necromancy pioneered by a serial killer--I could see possibly arguing that it's important to the narrative to show even the most seemingly trustworthy of Mages not incorruptible when pushed into a corner, although that's only sidestepping the out of character issue, not actually addressing it--the scenario is still stupid for being unbelievable. Are we really supposed to buy the idea that the most prominent Mage in the city, who is publicly outspoken about Mage rights, and consistently argues with his Templar keepers, was able to, while under the watch of a paranoid religious tyrant, sufficiently research and practice an almost entirely unknown form of forbidden magic in total secret? I realize that the game shows a lot of Mages being able to learn forbidden magic without the Templars catching on, but this guy is the most well-known, influential, and politically powerful Mage in the city. You can't tell me Meredith wouldn't be watching him like a hawk!
Oh, yeah, speaking of Meredith. So, after beating Orsino, you'll have to fight Meredith, the final boss of the game, whether you're allied with her or against her. This is a more believable scenario than having to fight Orsino no matter what, because Meredith's obviously so nuts at this point that she sees enemies everywhere, even in allies. The problem, though, is WHY Meredith is crazy. While the little information the game's given the player over its course about Meredith has always implied that she's pretty paranoid, she only got really crazy recently, and the reason for that is now revealed. It is--GASP--the red Lyrium Idol's fault! Yes, the Lyrium Idol, that made Bartrand go crazy earlier in the game, was purchased by Meredith and forged into a sword for her, and that has made her insane and obscenely powerful!
How does the Idol do that? Why was it made? Who made it? Is it malicious, or just inanimate rock? Who knows? Maybe Bioware. Certainly not we, the gamers, because if Bioware does have any concrete ideas about the nature of this plot contrivance of theirs, they're sure as hell not interested in sharing them. This object contributes in a major way to the events of the game and the final conflict that the game's meant to lead up to, and all we know about it is that it glows red and people become assholes by touching it. It's basically Bioware saying, "A wizard did it. A rock wizard."
Ugh. So anyway, final battle happens, it's all epic and over the top and everything that a final battle is, and of course, to emphasize how epic it is, all of Hawke's friends are allowed to fight--those not in the party will be computer-controlled allies on the field of battle. Decent. And much with Dragon Age 1's final battle, other NPCs start to show up as the battle goes on. Cullen, a Templar who recognizes that Meredith's brain is buggier than Fallout: New Vegas on its release day, assists Hawke, and Donnic, one of the city's law officers, may also come to Hawke's aid, provided that you had him and Aveline hook up and Aveline's still with you at that point. These are fine, they make sense, NPCs who have a stake in Hawke's victory and/or feel a personal connection to 1 of Hawke's party. But others who can join in the battle are Zevran and Nathaniel.
Zevran and Nathaniel are party members from Dragon Age 1, Zevran in the main game and Nathaniel in the bland Awakening expansion. In DA2, Zevran is seen briefly during a side quest, as is Nathaniel. While you can assist each of them during these sidequests, their presence in the game and connection to Hawke and the city of Kirkwall are, frankly, completely inconsequential. Nathaniel I guess I could see having some slight stake in the battle if Carver or Bethany is a Grey Warden and thus his comrade, but that's a slight stretch. And Zevran really just doesn't have any reason to be there. Seems like they were just grasping at straws for someone else to throw into the final battle.
Varric: And that's about it. No one knows where Hawke's been for ages now. None of his/her companions have stayed with him/her, except (Insert Romantic Interest's Name Here). Also, I don't feel like relating what any of Hawke's companions are up to now.
Interrogator: So you've taken up days of my time spinning this yarn about Hawke just so you could tell me exactly dick about what I really needed to know, which was, y'know, what happened to Hawke and where he/she is now.
Varric: Yeah, pretty much. I know you probably could have been dealing with this whole religious and social revolution that's been going on as a result of Hawke's actions, but I apparently have got nothing. You'll just have to be satisfied with a conclusion that isn't in any way conclusive. 
Interrogator: Please go away.
Varric: You betcha!
Interrogator: Yeah, so, that was extremely disappointing.
Leliana: Oh, WAS IT? Or is not knowing what happened to Hawke, combined with the disappearance of Dragon Age 1's hero which has been very barely referenced until now, ACTUALLY a way of AWESOMELY implying that there's more to come, something on the horizon so epic that both Hawke and DA1's hero have perhaps secretly left to team up against it maybe?
Leliana: ROLL END CREDITS!
Yeah, rather than give any conclusion whatsoever to this damn game, Bioware just puts a couple more carrots in front of our noses. None of the major issues of the game are settled, what ended up happening to pretty much all the important characters is never addressed,