Well… I don't know for sure that they've been erased; it depends on whether the N52 Teen Titans still happened. Given that both Tim and Cassie were on that team, it's possible that it did. And as much as there were large elements of that series that I personally didn't like, my feelings these days are that removing stories and even entire runs from continuity is a bad thing, and should only be done as a last resort.
That said, both Bar-Torr and N52 Kon-El were shuffled off the stage before Rebirth (Bar-Torr returned to the future, and Kon-El abandoned the team to serve Harvest), and neither has been mentioned since.
And “it happened, but hasn't had any lasting impact” isn't much different from “it never happened”. So unless and until the N52 Superboy and/or Bar-Torr get referenced or make an appearance, they might as well be “retgone”, as you put it.