I'm going off of ArenaNet's own admission, and the fact that they're against trivializing content, so based on ArenaNet's statements and design philosophy I came to the logical conclusion that a level 80 going back to a starting zone and being down scaled to level 10 (although the "starting zones" go up to level 15) wouldn't be able to AoE-one-shot everything like a level 80 in WoW going back to a WoW starting zone.