If you head north fresh out of the Vault, there's a viaduct with some raiders that can quickly kill a freshman player. There's also a barn where a Mr Gutsy can spawn in a random encounter. If you're really unlucky, Talon mercs can spawn there right away too. Head too far south and one reaches Fairfax Ruins, where there are lots of raiders with assault rifles and rocket launchers.
So yeah, it can be pretty hard alright for kiddies that came from Oblivion and expected the same type of level scaling.