The dialogues are stored sentense-/part-wise as MP3 and indeed you could open the game resources with the tankviewer from the toolkit.
However the file names are rather cryptic - act and talker are recognizable but nethertheless it will be a big puzzle, only combining the data from the conversation trigger/'trap' with the conversation list can give exact information what fits together.
Side note about using mods - sadly GPG hasn't found a good mod concept allowing customizations while preventing online cheat matters.
Mods now will turn the game into a different game version and you can not go on using your old savegames - but fortunately there is a tool called
All*Saves importing them automatically at every game start.
Well this is no invitaton to use mods now - it's an invitation to complain at GPG because the game is far below its potential - some things like the green ring have become even worse than in DS2beta.
I mean on one hand there are so many party conversations (that cost a lot of money for speakers and editing), on the other hand there is no official patch to ensure the gamer always can listen to them...