Problem with RDF in WOTLK

Hello all, I just started gearing my DK, it already have 3.8k gs, but when I try to join RDF HC it says that I don't meet requirements for the dungeons, and when I go into the specific dungeons tab, it says that I must obtain better gear to join the Heroic dungeons, the only item that I have that it's not meant to be used by DK's it's the wrist, because currently I don't have any better, I don't know what the problem is, but I've already seen a lot of people with 3k gs joining RDF HC, why me, with 3.8k can't join?

I don't know if I'm doing anything wrong, if someone could help me, I would really aprecciate it.

Best Regards,
Zulogh