I picked up Ekko a bit after he came out and I started ROCKING with him top lane (comparatively, I'm still a scrub). He has all the tools he needs to do his job. Hit and run tactics backed up by the ability to get in (e), get his damage off by getting 3 stacks (e hit, throw q, either auto or let q return do it) and then his passive adds damage for it and gives him the movespeed to get out. His w lets him trade during this very well, as well as having a requirement to land it well in order to get the benefit. Teamfights are a little harder, but if he gets his w off, the shield is large enough by that point that he can get in, either delete a carry or damage a few people, and retreat back out again without dying. You have to play it right though. He feels very good and he does his job well.
I got Fiora right after the update. Played her a bit before then, but really started trying her after. Compared to Ekko (who I play top lane, so this compares even better) she does not have the kit to do her job. She's squishy like Ekko, and her vitals mechanic, as well has her burst of speed (now bladework I think?) is 2 hits quickly instead of a lot in a row, suggest a hit and run style as well. However, she does not seem to have the tools to do her job well.
She gets in with her dash (Love this ability by the way, favorite part of her new kit as simple as it is), hits her e, first hit slows the target, allows her to move to vital side to do more damage with the second one, and then... how does she get out? She could riposte the incoming damage- but she's staying still while she does that. All she can do is walk away. Later on, her q is on a short enough cd that she could probably dash in, hit like above, and the reduced cd will let her dash out. Maybe. But what if she's fighting someone like Darius? She does her damage, meanwhile he's applying stacks of bleed with his autos, and when she's done, she goes to walk out. He pulls her back in, hits an enhanced auto, then the q as she's -walking- away. Sure, maybe she can riposte it, if the timing is good. And if the Fiora is good, she probably can. But the bleed will still hurt. And if Darius has sustain, she's actually going to lose long term because of the bleed, not to mention if she misses riposte one time, it'll really hurt.
She doesn't have an out, is what I'm getting at. Your suggestion of having her Q reset on vital hit is exactly what I was thinking. Q in, first e slows, second e does big damage to vital, riposte works somewhere in there, and Q gets her out again. Bam, you have a hit and run champ. It would also help her in other ways. Her ult, getting all 4 vitals can be a little tricky. 1 is a breeze. 2 is pretty easy. 3 is manageable. That 4th can be a little bit of a problem though. If her Q reset, she could be dashing all over the place, moving deftly and quickly around the battlefield to strike at her opponent's weak points- like a fencer. Bam. Identity.
Team fighting is another big problem. While I understand that part of her identity is as a duelist, and she should suck in full teamfights. That's okay. I get that. Theme. Role. That's cool. But she isn't just bad in full teamfights. Unless she manages to get her ult off and fully activated, or she finds the adc in the back and their team just straight doesn't notice, Fiora dies. Fiora dies quickly without accomplishing much. Extra dashes could give her the mobility she needs to not insta-die.
Of course, this would be a pretty big buff. Maybe decrease the damage aspect of her Q. Make it for the mobility. I dunno, I'm no balance designer, I don't know how much of the power budget that would take up. I mean, lots and lots of dashes on effectively no cooldown as long as a single condition is met, giving insane mobility seems really powerful, doesn't it? 
