I'm willing to stick with a show with a rocky start if I like the characters. In fact, most of my favorite shows started out weak but the casting and characters made me hold on until they found their footing and the writing got stronger.
the problem with so much of these mystery epics is that they have poor casting, bland characters and more often than not use characters as nothing more than cogs in the larger plot. It also doesn't help that in their zeal to go overboard with mysteries and plots they don't take the effort to actually develop them into something with some meat on the bones. I miss the days when writers would tackle two or three linear parallel season long standalone arcs that got some room to breathe and have a nice build up and satisfying payoff rather than a string of twists cliffhangers and far too densely plotted stories.