Regarding Cullen and what he knew/didn't knew.
I personally wish they had expounded on this. Instead DAI gives us a Cullen who's just sort of generically sorry for the bad stuff that happened. But oh he's learned a lot since then and he's a changed man now. Go mages! etc. etc. It's such a cop out.
I agree. I wish they had addressed his compliance with Meredith and the trauma and PTSD that fueled those years of compliance in the game instead of dancing around it. Trying to half-heartedly excuse and retcon it away.
I would call it a stretch to say he's "go mages!" now. At the beginning of the game he's very emphatically for going to the Templars for help, and expresses some of his old distrust against magic, very step of the way. First meet your advisers at Haven? Cullen recommends Templars. Cassandra points out how "we need power... enough magic poured into that mark--" he replies "Might destroy us all! The Templars could suppress the Breach." Come back from Val Royeaux after Templars go rogue? Cullen recommends looking into it. Heck, after getting back from your visit to Redcliffe (if you made it) if memory serves Cullen still recommends quitting on trying to recruit the mages approaching the Templars instead. My gal was thinking, "Dude! I'm an elven apostate who's expressed strong interest in going to the mages since the beginning, and I just found out a Tevinter magister and his officials have hulled themselves up in Arl Teagan's estate. We're not going to the Templars! Let it go!"
I would have actually PREFERRED a Cullen who, after some pushing and shoving, admitted that he DID know about some very SPECIFIC evils/wrongs that were occurring. That he wrestled with that and still suffers from the guilt to this day. That he tried to justify his decisions or turning a blind eye to horrible things. That he admits he was WRONG and that maybe, despite everything, he still harbors some prejudices, and some anger, YES! because of the torture and abuse HE suffered as a young man. How he continues to wrestle with these issues, etc.THAT'S an interesting character. That's the Cullen I fell in love with (not like that lol) and just found so fascinating. That's the character I really wanted to romance, to explore in a complex relationship (which is why I never wanted to romance him with a mage; same with Fenris). Fortunately BioWare spared me the opportunity to do so 
I actually kind of agree, even though I'm not really fond of Cullen's anti-mage side. (I understand why, but that doesn't mean I like it.)
At the very least, I wish the Inquisitor (especially a mage Inquisitor) could call him out on his service to Meredith and basically demand that he explain himself, and for Cullen to explain and address what he did instead of his usual pussyfooting around it. I'm almost annoyed that even though the Inquisitor can be a pretty ruthless jerk to a lot of our companions and things they care about (Sera and her trauma regarding cookies, Solas' love of spirits, Dorian and his issues with Tevinter/homosexuality, etc), yet the game almost forces you to coddle Cassandra's feelings about the Seekers and Cullen's history with the Templars. "Oh, he's really sorry for what he did." GOOD. He should be sorry. That was a horrible thing to support for all those years.
For the most part I do like Cullen as a character, but that's a really huge issue for me and I wish the game would address it head-on instead of keeping it around as this big, awkward elephant in the room that we're supposed to pretend isn't there when it is.
Very strange take on both Cullen and elves. I played through DA:O twice as an elven mage, and never once did I get the impression within the Circle that elven mages were treated differently. We do have the examples of Orsino and Fionna (sadly, very poor examples) to suggest differently. I have real issues with the victim blaming of elves that has been increasing as the games have gone on, and the fact that the two most powerful elven Circle mages both show such devastatingly bad errors in judgment doesn't encourage me (actually, when you add Solas and Marethari and Zathrian and even Merrill, has there actually been an elven mage they haven't made out to have horrible judgment - Merrill if only for her use of blood magic?) But they didn't seem to face any barriers that human mages don't.
But Cullen...Cullen is about the only one besides Solas who doesn't pressure you about Andrastrianism when you play a Dalish and seems prepared to take you at your word and clearly has his own deep doubts about the Chantry. He's completely supportive of you taking Dalish vows if you romance and marry him. He doesn't ask you to change your beliefs or culture. Sera does if you're Dalish. They didn't exactly have a huge amount of content, sadly, to get into as much as most of us would have liked, and no, he never asks you much about your culture or background (he doesn't for a Trevelyan either, does he?) But if you ask him about whether being Dalish is a problem, he actually says "I hadn't considered...elves weren't treated differently in the Circles I served. I didn't think what it might mean to you. I hope that doesn't - I mean, does it bother you?" He ASKS. He doesn't assume that you might not have a problem with him being human. He grew up in Honnleath and may never have had contact with a Dalish or even many elves before leaving to join the Templars. He's also the person who chews out the guy in Haven who apparently insulted Charter for being an elf...
So yeah, I find that particular rant baffling.
I think the first game kept it a little vague as to whether elves received prejudice in the Circle for being elves, and how much. If you play Amell and Eadric barks at you to get out of his light, there's the potential to respond, "I don't take orders from elves." If you play Surana and talk to Duncan before escorting him to his room (after that he stops talking), he'll discuss how unfairly mages are treated, as well as elves, and ask if you've received any prejudice in the Circle for being an elf, and you can give a number of responses: No, not at all. Yes, a little. Yes, all the time. Etc. So it was almost "player's choice" in that regard, and the subsequent games haven't strongly confirmed or denied it one way or another.
They seem to lean more toward "all mages are treated equally in the Circle, regardless of race" approach in subsequent games, but I personally find that a little unlikely. Cullen says elves weren't treated any differently in the Circles he was at, but I don't know... it's possible it was more covert (again, one apprentice saying to another, "I don't take orders from elves"), or subconscious and he didn't notice it because he's a human Templar, or it happened when he wasn't around (who knows how Templars who routinely beat and tortured and raped mages in private treated the elven ones), etc.
But either way, even if he didn't see elves being treated particularly badly in Circles (whether it was there or not), Cullen is shown to be a pretty good guy who is aware that elves aren't treated well outside at least, and won't tolerate that nonsense. Calling that one guy out for using a slur against Charter. Etc.
I even like the way he described the elves who joined the Qunari in DA2. Considering the Qunari attacked Kirkwall and many elves aided them, it'd be easy to be bitter about them. But instead, he kindly explains, "elves who joined the Qunari to find a better life." Good man. I like how he acknowledges that they got a bad lot in Kirkwall, and that they didn't join because they were traitors or ingrates, but were just trying to find a better life. I don't even know if I'm that understanding, and I'm obsessed with elves. (I gotta admit, after Trespasser I was thinking of the elven Qunari and Fen'Harel spies, "You ungrateful rats! After all I've done for you and our people!")