Isaak didn't run back to the Motherland after he killed the Columbians -- it was almost like he wanted to get captured. He can't be let out on bail because he's accused of a capital crime, and there's overwhelming evidence he killed those guys, so why is he so calm, collected, and bloody smug?
Dexter, as usual, is showing no fear, even relishing the battle, and that's in character for him. But it does seem as though he's becoming more reckless with each season. Perhaps that's intentional on the part of the writers and is intended to juxtapose his growing humanity with his increasing risk-taking in his night job. As he gets better at one, he gets worse at the other. It that's what their overall story arc is, I say bravo! But if they're just running out of plausible plotlines and are themselves getting reckless with the writing, then boys, it's time to call it a day.