Agent of the Lord Dragon worth it?

By Saithor, in Dark Heresy

I was looking over the Lathe Worlds expansion and spotted the Agents of the Lord Dragon alternate rank and was wondering if it is worth taking over any of the ranks of the regular Tech-Priest Career path, and if so, which rank is it best to take it at. I was planning to do it at 4th, but if that means that I miss out on critical abilties or skill ranks, I'll take it at a later rank. Thank you in advance for the advice.

It seems bad for a tech-priest because you lose out on too much.