+1 for Taveuni area.
The area would include Taveuni, Qamea and Matangi. Resorts range from expensive to reasonable. More resorts are located on Tavenui than the others. If you have not already done so, I would also look at the posts on this board in the Australia, NZ and the Pacific Islands link then the Pacific Islands link (under the Regional travel section). There are quite a few threads and reports on where to stay/dive. Note that my comments are land based not liveaboard recommendations.
These locations (above) take longer to get to. Viti Levu (most likely)then flights to Tavenui then maybe a boat trip. If you choose Taveuni, make sure to visit Tovoro falls (aka Bouma Falls). I think Sundays was when the local kids were allowed in free so it can get busy but the kids know where to jump in off the small cliff/ledge on the lower falls (1 of 3).
Many of the resorts in the Taveuni area are not dedicated dive resorts but do offer diving via in house ops or you can arrange an outside dive op. Some like Matangi Resort are more for couples (not necessarily romantic getaways but not dive dedicated like Beqa Lagoon Resort) but we did dive alot with Matangi's house shop.
In all the years of reading dive reports for Fiji in general, I can't recall reading one that said any site was bad or not worth diving.