One thing I feel should be brought up is that dragonflight's idea on how long the Warden was out for after the events in Ishal isn't all that outrageous. Morrigan says your wounds were severe and they were so bad that Alistair thought you were dead for sure.
Even with magic, that doesn't mean you're going to be able to make an instant recovery.
I'd say the travel from Flemeth's Hut to Lothering is a full two days (which isn't a long travel time for an era such as this) given that refugees have been streaming into Lothering from the south for two days because they lost their homes. In addition, Sten was sent to investigate the Blight and camped with his comrades around Lake Calenhad, where he was taken by surprise. Now, if we assume the Qunari learned of it within the first three weeks that it was going on -- that is to say, when Duncan first gave the King the news -- through one of their spies, Sten would've been sent south in this time.
He then awoke in a farmhold somewhere near Lothering after he passed out, but without his sword. In his confusion and emotional turmoil, he killed them, but "waited several days" for the knights to arrive so he could surrender. He then went three weeks without food or water when he was in the cage.
So that's three weeks plus another three weeks. Month and a half.
Within that second three weeks we were out cold with severe injuries that made death seem likely. Indeed, recruiting Leliana has Morrigan wonder if "our skull was cracked worse then Mother [Flemeth] thought" -- a joke meant to indicate the silliness of what we're doing, yet the addition of Flemeth and worse indicates we did suffer such -- which means that was one of our injuries. So dragonflight's time estimate of a week isn't too bad.
If it takes us two days to travel to Lothering, I'd hazard a guess it would take Loghain maybe five days to a week for him to get to Denerim, where at this time of the year (late fall/early winter, as soldiers at Ostagar remark on how it's getting colder) the Landsmeet is going to happen. He'd have a headstart over us as well.
however, we'd also have to account for the time frame it would take Duncan to travel from individual areas. If he recruits a DN, chances are the Deep Roads will exit somewhere near the base of the Frostbacks. I imagine they'd take Sulcher's Pass which, though dangerous, shaves a full two days off the journey into Orlais compared to Gherlen's Pass. As Sulcher's Pass can head through Redcliffe, this would allow him to head there and see Eamon and find him well.
From there, it's perhaps 3 days max to Ostagar.
So let's see
first 3 weeks - Battling the Blight at Ostagar. I suppose by Cailan's smile at Duncan being there that Duncan was never at Ostagar to begin with during these 3 weeks, but rather sent his recruits on ahead without him.
two days maybe for SP, then three days for Redcliffe to Ostagar, followed by one day for the battle itself.
This leads to a week of unconsciousness for Flemeth's hut and then two days travel to Lothering. Within that week Loghain meets with Jowan in Denerim and when we arrive in Lothering on the 2nd day of travel (or just shy of it for the Dog encounter) he makes his statements in the Landsmeet.
Jowan's then in Redcliffe where he tries to tutor Connor (he says he didn't teach him much) but also poisons Eamon. Eamon falls gravely ill where he clamors for water more and more, Connor succumbs to the Desire Demon's offer, etc.
I dunno. There is information in the game to make a timeline of events that works, but with Bioware having gone "one whole year" things get screwy and far too condensed. It's better to work out if we say 2 years, or 18 months minimum.
What other Bloodmage do we know that could have done that? (<== Not actually supported by in-game evidence.)
I hadn't considered that actually. It's always been my belief that Uldred led Jowan to blood magic covertly using the latter's jealousy towards Amell/Surana and then ratted him out (that theory at least has some evidence behind it), but Uldred telling Loghain about Jowan would make a lot of sense and support just how the Teyrn used him, more then just a chance encounter with him after he was caught and then brought to Denerim.
Uldred would've mentioned it and Loghain would've had soldiers patrol the roads for him after Ostagar failed, especially with word that Isolde was seeking a tutor for her son (and Loghain himself believes Jowan couldn't have gone in there so easily if Eamon was truly unaware, that Eamon had to have known Connor was a mage given who he is) and tried to deal with it then.
That actually helps settle the timeline issue and supports post-Ostagar. Granted, as you said there's no in-game evidence to support it, but it would work in a neater fashion then just "Take our word that Loghain's men got lucky"