I'm guessing from the expression "checked the integrity of the game" you're using a Steam install.
I refuse to use Steam for any game if I can possibly avoid it. Try uninstalling the Steam version and installing the EA/Origin one. Your product code is valid for both (plus all the DLC you've purchased), so there's no additional charge. Just keep you characters/saves when you do the uninstall.
Nope, the game is on Origin, and was from the start. Origin allows to "repair installation", if my memory is right, which is what I meant. DA2 isn't even available on Steam, they only have Origins, btw.
Never heard/seen this behaviour before, and I've installed from disc and Origin onto both Win7 and Win8 (multiple times. Long story...)
What mods?
What mods? What do you mean? I haven't installed any mods up to now, if that was your question. I only have the clean versions of the game & DLC. I find it strange that all DLC are missing text, why would that be? I haven't found any solution no matter how long I looked. I think I'll start Legacy without subtitles nor dialogue options, and hope that there isn't much dialogue cutscenes in it... =/
EDIT: also, noticed that in the Achievement panel through the main menu, none of the DLC-related achievements have a description. They're just blank, with the normal shield picture.
I have the exact same issue. I play on Win8 (I HATE win8) and I bought a physical copy of DA2, but I bought Legacy on Origins. I do not know what to do about this bug ☹️
