This is on the PC version, so I'm going to ask anybody who has beaten the game if they have encountered this. 
 
Okay, so I got to the landsmeet and I beat Loghain. After I beat him, I told Alistair to kill him, so Alistair cut his head off. So off we went to the battle in Denerim and it asks me who I want in my party, so far so good. Then it asks who I want guarding the back or something like that, and one of the options was "Loghain can do it" so I obviously chose that because I was just thinking "What?" then my character looked down at the ground and Loghain started talking but he was not there. I thought that was slightly odd, but I continued on. So when I killed the Archdemon and we were all having the celebration, I noticed that Loghain was standing over in a corner and I talked to him and he went on about some stuff about the battle. I thought this was getting weird. Then I went down the hallway and I noticed Zevran was also there. But I've also killed him. Along with those two dead people at the celebration, right across from Zevran was Wynne....whom I killed. Zevran also talked during the battle in Denerim at one point, but was also invisible like Loghain was.
 
I gotta say, it was a glitchy ending. Nothing groundbreaking or gamestopping....but my god. I didn't understand what the hell was happening when I was talking to Loghain when he was supposed to be dead and he was invisible.

Blood magic has some very interesting unintended consequences. 
 
Actually, I haven't encountered any of these problems... my Wynne was still alive, as was my Zevran.  For Loghain though I killed him myself and he did not rise from the dead to assist me against the archdemon.
 
I have had some minor glitches though in my codex, for example my entries for Connar and Isolde say that Isolde died in order to save her son, but I had done the alternative (saving the mages and getting them to help with the ritual so no one had to die) way.  A friend of mine who did kill Isolde for the ritual actually had his saying he had saved Connar without killing anyone... so it was basically showing the entry for whichever scenario you didn't use.  I can't really blame Bioware for stuff like this though, the codex is massive and I'm surprised as few mistakes occur in it. 
 
As a general point I did find that the ending sequences weren't as well done as I would have liked game mechanic wise but story wise (barring people rising from the dead to fight at your side) I still found it to be very satisfying... well the ending I got anyways.

" My ending froze.  I got to the part where the narrarator said "but at what cost?" then during the next loading screen my game locked up.  I'm doing another playthrough before I go back, if I go back, because I'm pretty sure all I missed were the credits.  At least I hope.  I didn't want to do that last battle all over again for some scrolling names, you know? "