As someone playing an archivist in a current game that assumed fairly easy standard divine scroll access (ie no unusual ACFs or the like, but domain, paladin, ranger, and druid scrolls were reasonably accessible), Archivist has just as much game breaking potential as a wizard. Of course, that's its upper potential.

In a world where standard cleric and druid scrolls are the only ones easily available got for them to scribe, life gets a little rougher, and you lose a lot of fun spells that already never see the light of day.

In a world where scroll shops/libraries are not a thing, you're down to the same danger that a Wizard has, trying to pick the two most useful spells to scribe each level, and praying (hah) that you find a divine scroll with something besides just core spells on them. That's a lot rougher of a place to be, but it's the same rough place a wizard would find itself in a similar world.