It always felt to me their break up was a way to appease the fanbloggers, who don't always have the right idea on how to do things. This is especially obvious in season 2:
You don't like Makkorra?: Fine we'll have them break up, and then let Mako dick around Asami some more
One location is boring? (no it isn't): Fine here is a lot of the Southern Water Tribe
Not spiritual enough?: Here all the spirit you can handle
It's going to be a herculean and ultimately thankless task to write up all the ways in which letting the mob write the show ruined season 4 (which actually had potential), but lemme stop you there. By the time they were making season 2 season 1 wasn't out yet.
Those first two points also didn't "address" fan consensus in the way they would in season 3, the first with all relationship stuff just vanishing, the second with the plot moving around to new locations every other episode. No, season 2 was definitely a story told by the writers and not the fans.