Once again Houston has never been a sack guy, but his stats were outlined by Emery and others on here in the days after he was signed, his body of work this year has spoken for itself. Keep looking for the negative though, this is pretty amusing.
What happened to Houston this year is what happened to Allen, and Peppers and just about every DE that has had to play in Tuckers defense.
He was asked to play a strategy that limits the ability of the DE to get to the QB. The first thing they are asked to do is play a 9 technique (where as in most other 4-3 defenses, the DE plays a 5 or 6 technique.)
Moving them outside this far allows for separation to the OT's. This separation allows the Tackle to gain position and the pad-level advantage.
Second, because his interior line plays a 2-gap, (generally the 0 and 2 techniques) the DE's have respect the A and B gap runs and "pinch". What this means is they are required to read the play before reacting. They still also have contain responsibilities to off-tackle runs. Think of it like a Safety that has to respect the play-action (without biting) before committing to a receivers route.
In general, based on my studying of Houston and Allen, like Peppers and Wootton and several DE's before them, they have all played into the system and are executing the way it's designed.
There should be no confusion as to why the interior line is getting more sacks. The DE's will almost always be a step behind and at a pad-level disadvantage to the Tackles.
Unfortunately, our DE's are not crap, our DC is.