Maybe you can find something that you are looking for.
And if you ever succeed breeding one of exclusive dragons, please take your time to give comments below the blog.. so we can consider it as suggestion for another users to breed dragons from this category.
Got diamond dragon from breeding pure dark lvl 20 + terra lvl 11, lava dragon from breeding pure dark lvl 20 + fire lvl 10, great white dragon from breeding lvl 15 pure and lvl 7 ice dragon. From my tests and outcome it shows that only one of the parents need to meet the minimum lvl 20 requirement to breed these exclusive dragons, and I suspect it is easier using pure level dragons to breed exclusive (breedable ones) because normal hybrid + normal hybrid will always fail, at least for me.
Pure dark dragon can also act as Pure element, as I also got Pure Terra dragon from breeding lvl 20 pure dark + lvl 11 terra. Hope this helps.