Loghain makes sense to me, in general.
I just don't know why Hawke would be friends with him. I have to invent more about it. I can imagine more stories about that with Stroud...especially with Warden sibling.
This ^
Not questioning Loghain's presence in Orlais since he was supposed to have been assigned there after Origins. I'm just seeing the 'friend of Hawke' connection as tenuous at best, with all three actually. Alistair and Stroud at least would have had some connection to the Champion of Kirkwall since they actually meet in DA2, however briefly. Stroud has a bit more credibility since he would have been the one to potentially have saved Bethany/Carver--making more of an impact than a senior warden who helps out in a skirmish during a crisis then trots off to do 'more pressing warden business'. Alistair less so since he falls into the latter category and they meet for all of 2 minutes briefly during the Qunari attack. It would have been more credible if Warden Loghain had at least made a brief showing during DA2 in the role Warden Alistair fills, especially since it would have been impossible for them both to appear in this capacity.
I could even see Alistair's presence in Orlais as "encouraged to leave Ferelden" by Queen Anora, who would have probably made it difficult for him to stay, particularly on my King Cousland, as it would have been Allistair who killed her father and is still, alive, a potential threat to her monarchy.
But the connection to Hawke is far less plausible than why they are in Orlais. To me, Stroud makes the most sense if Hawke has a warden sibling since they have the strongest connection.
I guess Corypheus is the stronger factor in any of the three showing up at all and contacting Hawke since they would have learned about the ancient and Hawke's connection to him.
Time continuity is the worst part of Bioware stories. Hawke would have barely learned what happened and yet, as soon as you get done addressing the crowd in Skyhold, Varric tells you Hawke is waiting for you, and Hawke already has a warden contact. Prior to this, no one even knew Corypheus was the threat. It was the unknown factor. How could the Warden have 1) contacted Hawke 2) met with him enough to be called a friend and trust him enough to allow the Inquisitor into the equation 3) Hawke have even arrived at Skyhold practically ahead of the Inquisitor who only just arrived himself. Recall, Skyhold is still such a mess when Varric says he has someone to speak to you, you've barely opened the doors to the main hall, let alone cleaned out the pigeon poop.
Today, not a problem, information flies across the internet with the speed of thought, but medieval times, relying on messenger bird...I dunno, it seems iffy to me.