I think Gale's written to be mostly at fault of his own downfall. The other companions are not. Astarion maybe would have been, if his past hadn't been cut. Whether Gale's folly being his own fault is "right" or not is a different matter, but I'm pretty sure Larian intended it to be this way.
We all know by now that they're not very good at being consistent with their own narrative and themes.
