Texans D will be a force but if, and unfortunately only if, defensive tackle Seth Payne comes back and operates at 75% or better. The nose tackle in the 3-4 is that important and our defensive production dropped off significantly after his injury last year with backups not meant to be starters.
Think of the last two Super Bowl winners and you will find they had at least one dominating interior d-lineman (i.e. Warren Sapp and Ted Washington...and watch the dramatic difference they make to the Oakland Raider's defense).
The Texans defensive additions and shuffling, along with a clean health report, will produce a winner and dominant team.