Dumbledore appeared much more wielding the "idiot ball" than Voldemort in this final arc.

Voldemort initially needed Harry to have his wand for the Unbreakable Vow. Yes, it was a mistake to not remove the wand from him afterward.

He couldn't imagine Harry would be a threat with a wand without being allowed to speak or move it, partial transfiguration of carbon nanotubes or antimatter from the wand itself just was unimaginable to him, so it's an understandable mistake, but it does strike as odd when compared to all the precaution he's taking in "paranoia mode".