EverquestII will play just fine with a Radeon 9000 card as it has PS/VS V1.4 due to DX8.1 compliance. The DX9.0 is mainly for cards that are stuck at DX8.0 level with only PS/VS 1.1.
As far as DxDiag having problems, you need to try a couple things:
1) Find out what mainboard/motherboard you have and download & install the latest chipset drivers and AGP drivers (if applicable.. some include AGP with the mainboard chipset drivers).
2) Download Catalyst drivers from ATI's website. For EverquestII, I'd recommend the 5.2's... or if you play a lot of other games, the 5.9's.
3) Once you have these two things installed, run DxDiag once more. (Start menu/run, and type dxdiag)
In DxDiag, there is a button on the bottom for saving the information to a file. Click it and create a file on your desktop.. call it like dxdiag.txt or something.
If you can copy/paste the top 1/2 of that file here, it will yield insight on what you need to do next.