The 1900 number was based on if you had 178VIT. If you want to change this to be if you had 320VIT though, it would drop it to about 1800 DEF needed.
Trying to read both Treach's and your posts with as little bias as possible, I don't think he ever made the statement that the other stats were useless as in "they do absolutely nothing". His point (at least from my view) is that if you are making an optimal tanking build (aka "min/max-ing"), you have to make tough decisions as to which stats you should improve with gear - you can't have everything. So he's not saying all stats other than HP have no benefit - he's saying that the benefit from stacking other stats is so small relative to the benefit of HP, that you would never stack them over HP. Because this is the case, you could say it is "useless" to stack say DEF on high end mobs. And he would be right - it is "useless" in the sense that a much better build exists.