Rahvin gets killed by a pretty pissed off Rand, I figured that would have disastrous effects, or maybe they don't mention it until next book. ALSO, it's a bit confusing, I understand they get killed to the point that they don't exist in other people's heads (that was shown by the darkhound biting Mat but not really biting him due to the balefire erasing that history and some people aren't sure about a darkhound attacking), shouldn't Nynaeve have been wondering why she was there in the dream world with Rand, shouldn't people have forgotten about Rahvin at that point? Shouldn't some of the damage he have done been reversed, or maybe he just completely ceases to exist [unlikely since he's thousands of years old], but still, see where I'm going with this?)
I guess I wish they made sense about strong balefire is exactly, it often just gets cited as a bar of light and sizzles with motes of light fading. But I don't know exactly how strong that is, and how damaging it is to unravel days, months, years? of existence.
Balefire doesn't completely remove what it hits from ever existing inheriently. Basically only a certain amount of their existance is undone, how much is determined by the amount of power used. So you may only undo the last five minutes, or the last five hours, or even the last five years, it just depends on the amount of power used. It always goes back directly in time, so if you erase five hours of existance, it removes the last five hours, rather than some random five hours.