I was running antorus today, I didn't experience it much on legion, it use a lot of portals which is bad but the design is one of the best I have seen, it is really a diabolic tower, it reminded me of some towers on l2, it would be much better without so many portals and more focused on a tower design. It is probably the only raid of legion with a decent design, the rest were total crap. Hellfire citadel was supposed to have a demonic theme as well but the design is ugly imo. Brf or highmaul were much better than hellfire citadel. Hellfire citadel reminds me some classic maps of fps games, the design is sooo generic.
I'd say my top 5 is:
Temple of Ahn'Quiraj
Karazhan
Throne of Thunder
Antorus
Ulduar
Others that I like too: Uldir, MC, Highmaul, Brf, SoO