Having played around with DimmDrive a bit, I don't notice any improvement compared to not using it with Everquest I.
It could be, that the game is older and the system is not pushed by it at all... I remember much poorer performance, when the game was current.

Logging into the game, and changing zones, is fairly quick (about the same amount of time) with my normal drives or the DimmDrive.
I've got a pair of OCZ Vertex 3s, in RAID 0, as my Windows/Gaming Drive.

I'd expect a large improvement over a platter drive.
But a ram drive should still be quite a bit faster than an SSD (or 2x SSD in Raid 0).