The argument of which round a 3-4 DE is drafted in is becoming more & more a moot point every year.
More teams play 3-4 Defense now than they did 10 years ago. The demand for a Brett Keisel was so low, he was picked in Round 7. In 2012, high 2nd Round selection Derek Wolfe is essentially Brett Keisel without a beard.
That Hood was selected in Round 1 makes little difference to the fact he couldn't beat out entrenched, long term starting DE's in Aaron Smith & Brett Keisel in his first 3 years. Hood has become a solid part of a rotation on a successful DL. That he doesn't stand out could be a good thing- most times a 3-4 Steeler DL stands out, it's because he's getting owned.
As for Hood to NT- he's really a 1-Gap defender, so doesn't really fit 3-4 NT as he'll only really attack between the OC & OG, where the Steelers will want a 0 Technique, 2-Gap type...Josh Chapman anyone?