For the most part, those 'unique twists' might have been a relic of the 1.0 version of those dungeons. Try looking for 'FFXIV 1.0 dungeons' to get an idea of the assets reused from 1.0 in ARR dungeons.

I found references to the fact that FFXIV 1.0 had exactly 0 dungeons at release. Only 1 of the 4 dungeons added later were lower-level (Toto-Rak, if I remember correctly, was a level 25 dungeon. The others were level 50 instances).