honestly if they just removed the MS from her passive she would be fine but the ms + a low CD dash just gives to much mobility because it means she can trade so much better even when behind in order to catch up because she can Q in for the passive proc then run with the speed boost, which might fit a duelist theme but its toxic as hell when combind with a very low CD Q
i think what they need to do for fiora is make her passive mark enemy champions in 4 spots like her ult does, buff its damage, but it only trigger its effect when she breaks all 4 spots, the marks on an enemy champion reset if she attacks a new champion or they leave combat
example make her passive deal 10% the targets hp max as true damage after she procs all 4 then it gives her 30/40/50/60% decaying MS (lvls 1/6/11/16) + 1% per 10 bonus ad for 2 seconds
her ult would trigger her passive at 50% effectiveness per broken vulnerable for 5% max hp true damage (20% total) and trigger a 15-30+% decaying move speed and when she breaks all 4 on her ult will deal the full effect of her passive (10% max hp true damage + MS) for a total of 30% max hp true damage as well as the heal which is now based purely on bonus ad (no base value heals for 1.5 bonus ad per second
what does this change do? it prevents her true damage from helping her evaporate squishes but still does a good chunk to tanks that can reset right after she finishes procking it now instead of the delayed reset
it adds more damage to her passive but makes it harder to proc while still making her ult a powerful tool