Based on an incredibly rough estimate that is probably incorrect: Something like 1 Dungeon if that's even what had been the replacement project. The majority of the Reaper work was done by Engineering (and, to a lesser degree, Art). They don't typically make content. Rewards have been handled by a couple from the dev team (none of our primary content people, though both have made content in the past) but neither spent more than half the update cycle on it.
Basically, regardless of the fraught method of my estimating: Reaper wasn't a large drain on content dev time.