Something next to normal, that's the thing I'd like to try

I don't think it's a question of "jumping the shark" (a phrase which is used so often it's completely lost all meaning) so much as it's a question of Homeland clinging to the things that made it so good in S1 (i.e. Carrie/Brody) even though they're no longer working. Breaking Bad is constantly moving forward, taking risks, escalating the conflict and letting its characters change, while Dexter stagnated, repeating the same character and plot arcs over and over because they're afraid to deviate from the formula that worked for them.

Homeland stagnated in S2 by doubling down on Carrie/Brody and Abu Nazir, retreading the same ground as S1. But they could easily bounce back in S3, since they've substantially shaken things up at the CIA, separated Carrie and Brody, and eliminated Abu Nazir.