Legend of Korra

What also doesn't work is the fact that A:LoK is never on i.e. there are never any reruns. Just this past weekend, there was an A:TLA marathon on their "sister rerun network" and it comprised of every episode of the series over a two day span. While I did not sit and watch every episode I did watch a good three hours or so and listened to another three hours. Even without the marathon, A: TLA is on daily, either one or two episodes on the same sister network.

I think it might just be the case that A: TLA is a better series and more popular. Not that Nickelodeon is doing anything to shift that imbalance.