Here's the quote from "The Making Of Star Trek Deep Space Nine" by Judith & Garfield reeves-Stevens, published December 1994, pg 242:
Every physical element of Deep Space Nine is shot on film, not videotape. However, that film is just a first step. As soon as it's printed, it's sent to Unitel Video, where it is transferred to D2 videotape. Then the film is put into storage and ---- provided no disasters occur while an episode is in postproduction --- it never sees the light of day again.
The film elements that are transferred include everything shot on sets and on location by the first and second units, all the passes of models shot at Image G, and all film of physical matte paintings executed by Illusion Arts. Live-action footage is also duped onto standard VHS cassettes so the producers can review them as dailies.
Aside from D2 and VHS videotape, no other videotape is mentioned as being used. Also, you have to remember Digital Betacam wasn't on the market til 1993 (D2 was out in 1988), so before 1993 tapes used for final mastering would've been Betacam SP, D1 and D2. Also, you have to remember that the Reeves-Stevens, even though they were not producers at this point, for their book, they still had unlimited access to the sets for the book. And if you watch the opening credits for DS9, when we get the shot of the underside of the station with the core, I did notice rainbowing right along the edges of the lower part of the core.
Also, how do you know that CIS went right to D1. Even the Cinefantastique article, from what I've read of it in regards to D1, seems to be saying that Digital Magic did have D1 decks at the time, but there was no specific mention of TNG actually being edited on them.