Re. the chance to talk to the Templars before starting their quest: that's in the first time you go to Val Royeaux. You see Lucius, he makes an outrageous speech that raises a thousand red flags, gets his sanity questioned by Friendly Neighborhood Good Guy Ser Barris, and then again by Cassandra. All the plot signals that there is something very wrong with the Templars are in that scene. Perhaps because it's too early in the game some people have forgotten about it by the time they get to Redcliffe? But you do get the same forewarning for both sides.
Wow, I really don't remember Cassandra saying that. Just, "Lucius was sure acting weird!" or something. I think you also don't actually know that the Templars are in Therinfall until you choose the map marker do you? Maybe in the conversation after Val Royeaux? I've also had a problem where both map markers were only showing green once, and the other times just the mage side with "DO THIS NOW" and giant arrows pointing to it. As the player, I had to know to choose Champions of the Just instead of the green foggy thing.
(Yes, still not a completed playthrough for me, but I've done each of those at least twice each.
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