Back in the day redistricting was even crazier. You could just draw an arbitrary number of districts with arbitrary population sizes. That seems bad on the surface. With this system, election outcomes could potentially be entirely determined by how districts were gerrymandered.
The efficiency standard seems like trick to get closer to proportional representation. All of this comes down to the 14th amendment being "one person one vote" rather than something like "all votes must have equal weight". A small language that has made things really complicated.
IMO just switching to proportional representation is a much cleaner solution. But the efficiency standard seems like a decent solution to keeping races competitive and from being severely gerrymandered.