Also, has anyone mentioned the possibility that the whole HoA prophecy was cooked up by Ruin? It seems possible that it has been lying in wait every age for the one person that would be able to release it from it's prison. First Alendi and now Vin. Maybe the prophecy is just another tool to lure such a person to the well.
Also, ruin only affects small things in clever ways, he doesn't change everything, I think this is for three reasons:
1) While trapped Ruin may not have had the power to change that many things
2) Ruin didn't know all the texts that were out there, he changes things as they come up, example, the Sazed Holy First Witness thing.
3) If he made such big changes (like creating a whole prophcey where there wasn't one before) People would notice, the only reason Kwaan is the only one to notice is because of his photographic memory, however, if Ruin made big changes that were noticable, anyone with a normal memory would notice. Kwaan says he didn't notice the changes until after he decided Alendi might be the hero.