I think these DD changes are just what Fiora needs

And some base tank stats to be toned down (and perhaps a lower AD ratio on Q).

Right now, the fact that Fiora has the base stats of a fighter and the liberty of building 2 tank items without ever really falling off in damage means she is very tanky for a melee carry. Add in her 32% lifesteal, and she's not only a drain-tank, she's a tanky drain-tank.

I think this is making her teamfighting and dueling a lot stronger than it should be, as she doesn't melt as fast as she should, especially not when compared to a Riven who needs to build almost full AD to keep up in damage. Perhaps not burst, but Fiora easily matches other melee carries in DPS.

That being said, this DD change means Fiora is gonna really love the item, even taking it over BT at times. Her tank stats can be lowered because the damage reduction is a lot more potent and gives Fiora an opportunity to heal back damage. Even better, she won't be building 2 tank items, only the standard 1.

However, this comes with problems of it's own, specifically, 30% damage reduction and 48% lifesteal are gonna make her way too tanky. Hell, maybe she'll just replace BT and stick with the 3 damage items 2 tank items. So I think her base tank stats should be lowered so she doesn't become too tanky, and perhaps the AD ratio on her Q should be lowered so she has incentive to get 4 AD items, not just throwing out BT for DD.