Yeah, I was pretty disappointed too. Trailers made the story out to be way more interesting than it turned out to be. Also, wtf is up with Kazumi? What even is she? How does she know Heihachi will cause destruction? Nothing about her is explained. And we don't find out where the devil gene came from like promised. We just find someone who had it before kazuya, and its still not explained what it is or where it came from.
Also, good lord that narrorator was not interested. He made peter dinkledge in destiny sound exuberant by comparison.