I agree, it's remarkable how a game can manage such flowery, perhaps even pompous writing, and yet it never seemed to step too far over the line. I'd also agree with
@moocow in it being the voice acting that manages to sell the dialogue and keep it consistent. Funnily enough, Simon Templeman, voice of Kain, is the same voice actor for Loghain; it's no wonder that they're both interesting and memorable characters. Another thing, the "dialogue wheel" is perhaps the greatest blight on RPG's beside voiced protagonists. I didn't really like it in Dragon Age 2, but at least Hawke had a good voice and could be a right prick at times, I cannot say the same about Veilguard's protagonist though.