Yep, I did the 'didn't change out of formal gear' too, but I did it again when you enter that area after you've re-equipped your companions and you have to give Quizzie back their gear. Really happy I noticed before I entered the last room.
I'd heard about the dragon in the Hinterlands and how people kept finding it before they could fight it and getting fireballed. I couldn't find it. I looked around out of curiosity but never found the area. I was wondering where it was because I'd done a good deal of walking around and hadn't seen it. Then I did the quest that leads you to the camp in front of the area, went 'Never seen this before' and got slammed when I got out of the cave. Thank goodness for barrier.
Couldn't figure out how to upgrade Bianca until I saw the character tab at the top of the crafting screen.
And for some reason I didn't realize that killing the (spoilers for Solas' personal quest) Pride Demon in All New, Faded for Her, would kill his friend (it attacked me and... stupid) I got rid of the pillars but nothing happened because I didn't realize that I missed one at the back so I figured that it would end the battle. It did but I had to reload because I figured that killing the spirit was not the best outcome.