Hank is a good cop, but he has no reason to suspect his new office in the DEA's secured building would be bugged. One would expect the room to be locked, and the building to be well-guarded and monitored. He also has no reason to suspect Walter of any wrongdoing at this point (or, at least, is letting his personal feelings cloud his judgment). I give that element a pass.
I'm surprised this "season" is more than half-over at this point; it feels like it just began.