Also, did you guys notice that NOBODY in Asunder or TME speaks about Meredith? Everybody talks about how the Circle rebelled in Kirkwall, and that's all. So I think, maybe mages' rebellion was such a big thing, that everyone, including the Divine, overlooked the red lyrium problem?
For example, Cullen sent his report about what he saw. And in the end of the report he added that he realized he's made a mistake when he let Hawke go, because turned out Hawke was conspiring with the Grey Warden mage Anders, who blew up the Chantry. And now Cullen is going to try to find them and bring them back to justice. Divine reads that and says, "Ok, looks like this Knight-Captain knows what he's doing, Maker help him! Meanwhile, let's do everything we can to prevent other Circles from the same fate!" So, maybe the Divine was just too occupied with what happened next to deal with Kirkwall templars and Cullen.
I hope they won't handwave this, because I want the events of DAII to make sense to me!
And I want to know what happened EVERYWHERE, and what Cullen was doing, and all the stuff 
This is a really good point about Meredith. Indeed, NO one mentions her or blames her. Maybe that is what happened. Cullen gave his dutiful, probably dry and understated account of what happened, and some minor bureaucrat skimmed it, saw "BLAHBLAH MAGES BAD AND REBELLED" and took out his red stamp, "A wizard did it. The Champion, a known agitator, probably helped. It's over."
I don't think it helps that the Exalted Marches got cancelled, which was supposed to explain the events leading up to Hawke's disappearance. In regards to a Viscount Hawke, for all we know the DLC could've (for example) picked up 3 years later 6 or so months before Cassandra showed up in Kirkwall to interrogate Varric. Hawke would leave his post in Kirkwall to go deal with the issue and then whatever would've happened in this DLC would occur causing Hawke to have to go into hiding/get abducted/whatever, and his/her friends to scarper/split up and go their separate ways. Then all the really bad stuff starts to happen and the Mage/Templar war reaches fever pitch, causing Cassandra to track down Varric since he was the easiest one to find (and because obviously Varric is a major player in DAI, lol).
This is a really good point. Gosh, I wish we could've seen what happened in the expansion. I know we'll see some of the content... but certainly less. 
Makes me wonder if no one bothered to take Cullen's warnings seriously about the red lyrium idol/red lyrium in general, so he ditched the Templars when they rebelled and went rogue with his own little faction in order to try and take matters into their own hands? If that leak is true and there really is a militant faction working with us called the Red Fists then it's entirely possible that perhaps he (or the Divine, if he's working for her) decided to name the faction "Red Fists" as a representation of cracking down on the Red templars/red lyrium/whatever with an iron fist?
This is the best idea I've heard for why it would be called something dumb like the 'red fists.' I like it!
I think I always just assumed that Cass would've already spoken to everyone else involved. Especially Aveline and Cullen, who would have given the "official" report from both the city and the Templars. In my head, they had to hunt down Varric because you see him dragged into the room at the beginning, which gave me the impression of "Aha! We finally found the dwarf. Now let's see what he's got to say about it all..."
I would expect her to ask everyone... but honestly, she seems genuinely gobsmacked by Varric's story. I just can't imagine she'd heard all that before and just wanted act surprised for Varric's sake. Really, I think you're right that it's just a function of gameplay/storytelling. Varric is by far the best person to tell the framing narrative, even if it doesn't make a lot of logical sense.
(and BOO that we're talking about my very favorite topic right when I have to go to work...
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