The creators are seeing this and getting back to basics. The last two episodes have been really good. Friday's was all about a man who enjoyed being possessed by a demon and would go to any lengths to get it back. It was a creature of the week scenario, but it started with the Dean's obligatory call to Frank.
It's become a common practice to start the episode with a call to Frank to get an update to the Leviathan situation. The call always ends up the same way with no new information and the brothers can move on with the rest of the episode. It's a cheap way of telling the audience the Leviathan threat is still there, but we're going to focus on something else for now.
The first half of the season was very heavy on Leviathan, as they watched their ratings drop, the writer's had to put a spin on it and keep people interested. I suspect since the season is drawing to a close, the Leviathans will come back, but I don't expect it to be so doom and gloom. The one saving grace is that the next episode on March 9 features the return of Mischa Collins. The show's creators have said that he would return, but don't expect him to be the same ole Castiel. He's likely something or someone completely different.