a .4 bonus AD buff might seem huge...
But it really is not in the case of Fiora on the PBE.
How big of a buff is this?
say you have 23 AD from a Doran blade and runes.
This means that every time lunge is used against an enemy at rank 1 it does .4* 23 = 9.2 so 9 more damage is done.
It is less and less damage with each rank of the ability and unless the Fiora is able to get a drastic amount of AD before rank 7 this buff is negotiable.
A level 7 Fiora maxing lunge with 60 bonus AD is only doing 6 more damage for the 4th rank of the ability.
Yes they are buffing Fiora.
No this is not going to make her broken.
There's probably a good reason I haven't seen her but once in the last 3-4 months.