I have to admit JKR introduces the Deathly Hallows well enough by saying through Xenophilius: "You haven't heard of them? I'm not surprized." So though I think they should've had some presence since the beginning of the series, she covers her tracks enough with Xeno's line to only bring them in now.
Foo. One less thing to gripe about.
Foo. One less thing to gripe about.
lethargic
Another take on it could be that Dumbledore might have thought the wand as a last resort if they couldn't get the horcruxes, not knowing that Voldemort was going to be after it. It would give a powerful weapon if he had all three...