Let me restate then. I think it's a terrible idea if the intention is to promote any connection we have to our characters. I'll agree that having our characters take a more active part in cutscenes would be nice, and having us grunt or laugh or sigh or cough or whatever would be fine, but the very second your character opens his mouth and spouts off a two sentence statement, using sentiments you yourself would never use, I can guarantee that you'll feel less connected to your character. It doesn't matter if this dialogue is voiced or written, in the end the writers are choosing to speak for you, which just can't work. The only possible way it could work is if they gave us speech options. Mass Effect did it beautifully, with the vague "gist" statements on the wheel that led to a more in-depth and lore-friendly statement by the main character. Even if it wasn't exactly something you'd say, there was still some connection because you chose for him to go in that direction.
I didn't use the example of the other MMOs having failed for having done the voiced character thing, I simply meant that other MMOs did it and it doesn't work, in my opinion. I'm all for having Llen grunt hit in a cutscene, or growl in an angry way if some guy is being a jerk, or gasp in shock or express sadness at something horrific having happened. Character integration into cutscenes can be achieved perfectly well without having our characters see something bad happen, take a knee, and say, "Oh, woe! I can't believe something like this happened! I'm angry, and I will vow to make them pay. Whether they pay with coin, or pay with their lives, they will pay! FREEDOM!" or some such nonsense.