If you play *as* Gale, you're basically a Human Wizard Tav. You get a really fun cat in camp, but otherwise would never know that you're Gale of Waterdeep until the very, very end.
What if you reverse the situation, and play a human wizard Tav (or a githyanki warrior, since you also named Lae'zel)? What I find problematic is not the companions as characters, but their origins.
When playing as Gale, you can learn that
the soul can be restored by divine intervention after the mind flayer transformation. This puts the entire plot on a different light, especially that ending scene, with all the people in the city transforming. Your generic wizard Tav will not be able to learn this. And as generic wizard Tav, the only options regarding this powerful magical artifact that started it all are evil (use it or make a deal with a devil). Same goes for Laezel. When playing a gith Tav, if you go the free Orpheus route, Voss and others will praise Laezel and call her sister, but Tav is practically invisible in these conversations. Even that final scene you don't rate your own dragon.
So I can see how people can arrive at the conclusion that these characters were written mostly as protagonist. I think as with any impressions, this is of course very subjective, and dependent on your own experience, but it is not without substance.
On a side note, I also found the throwbacks to the original BG games in Gale's origin a bit of a weird choice, considering who DU is.
