I mean, first of all, "You are the harbinger of death, Kara Thrace, you will lead them all to their end," didn't seem like something the Hybrid said particularly more quietly than the rest of the prophecy she spoke which everyone who was in that room was discussing. So why didn't Leoben know about this?

Those lines actually were somewhat quieter. (I just rewatched.)

As for Lee getting Dualla's effects, I'm just worried about the radioactive jacks. :/