To me, BioWare's stories aren't so much "formulaic" in a negative way as they are "well informed" by fantasy and sci-fi norms. Many elements in the ME and DA storylines are paying tribute and homage to literature, film, and other precedents in those subcultures. Their head writers are actually some of the most talented in the videogame industry in my opinion. Looking at the actual dialog and characterization in these games, I think that's apparent.
As Qoheleth said so long ago: "There is nothing new under the sun." It's all been done before. Just about every work of fiction is going to contain elements that are recycled, especially videogames which are defined by the limitations of our actually having to play them. What do I mean by that? Well, consider the bizarre proliferation of barrels in sewer systems containing valuables. Or people who seem totally at ease with you wandering through their houses.
Even a game as revolutionary as Valve's Portal has plenty of cliches and formula.
I've always been struck with the sense that BioWare's writing team has a lot of fun with their writing. They're quite aware of what their past efforts have amounted to, what they want moving forward, and what their fans want. They use this to their advantage, and they use their influences and inspiration effectively.
