I have read that Governor Moulton, Professor Sargent, Rose Emery and Woodville Red are a little more resistant to dieback. Other info:

https://www.americancamellias.com/care-culture-resources/insects-and-diseases/camellia-canker-dieback

https://lee.ces.ncsu.edu/2022/05/diseases-of-camellias/

Several years ago I found and printed an online article by Bobby Green titled "You Say You Want a Revolution : Reinventing the Garden Camellia". Sadly, I can no longer find the article online where it is available for the public to see. In it he says, "The most useful, floriferous, compact, disease resistant cultivars of sasanquas contained camellia x hiemalis." Examples of these would be Mine-No-Yuki and Shi-Shi-Gashira and Leslie Ann. He talks about how Tom Dodd Jr successfully hybridized with C. x hiemalis cultivars to produce Alabama Beauty (syn. Mr. B), Jessica's Ruffles, Stephanie Golden and Reverend Ida.

Bobby Green owns Green Nurseries in Fairhope, Alabama. Until a few years ago, his nursery specialized in wholesale camellia sales, but my understanding is that the nursery part of his business is now closed so he can concentrate more on breeding. One of Bobby's stated goals in this paper was to produce plants with more "disease resistance - most significantly to Glomerella cingulata and Phytophora spp." In this article he lists some of his October Magic series as having C. x hiemalis -

October Magic Bride

October Magic Orchid

October Magic Ivory

October Magic Ruby

and also Suzy Dirr, which is noted for its exceptionally fast growth.

I don't know what year this article was written, and I am sure this is not an exhaustive list of more disease resistant camellias.

I believe that Kanjiro is also a selection of Camellia x hiemalis, and it is generally considered to be a plant that can live with less than ideal conditions.

Many people recommend planting camellias high and on a mound. I have read many times that planting a camellia plant too low will lead to a slow death, and I experienced this myself before I learned about planting them high. I personally like to use expanded shale in preparing the planting area to help aid drainage, which I believe is especially useful during times of high rainfall.