I don't ever even see Fiora in-game, and I can still tell you that she is in terrible need of a rework from a thematic perspective.
You see, a duelist is a fighter of finesse, of efficiency, of precision and technical skill. The words "feint," "fencing," "rapier," and "riposte" more often than not conjure visions of a very intricate martial discipline. Or Errol Flynn and Zorro. Which, to be fair, is still pretty intricate stuff compared to how Hollywood thinks other melee weapons were used.
What does Fiora's entire kit do?
An out of place passive, a "lunge," a deflector shield, a pinch of "derp, rapiers are fast," and a metric ton of multi-target damage.
Her Ult is actually the least thematic of her abilities, being a multi-target nuke, and thus completely contrary to the nature of the duelist as a one-on-one fighter. By your own admission it is also the one thing that makes her viable. Thus, she's prime rework material at best, as soon as Riot gets through the higher-priority champions, and flat out un-fun at worst for those who were expecting better of the so-called Grand Duelist.
Funny you should cite her lack of escapes, too. Footwork, you see, is very important in Fencing.