Bismark(lvl 57) was the hardest trial in heavensward, not because it was poorly tuned but because people couldnt pay attention and follow the 2 or 3 simple mechanics.
Susano'o(lvl 63) was the hardest trial in stormblood, not because it was poorly tuned but because people couldnt pay attention and follow the 2 or 3 simple mechanics.

You might find yourself thinking, nidhogg and shinryu had the most complaints for a nerf at release and both were more mechanically complex fights for their expansions. And this is all true. But once a certain percentage of the population got the fights down these complaints mostly ceased. Rising i-levels helped smooth the fights out, but the complaints settled down before this could have been a factor. Titania seems destined to be this expansions trial that will still challenge some players 4 patches from now when it pops up in a roulette, because for whatever reason they wont be able to pay attention and follow the 2 or 3 simple mechanics.