So my question is if she was having it would have make her OP? or it wouldnt change anything?
I'm not sure if it would change that much.
All of Katarina's in-kit damage is magical, which has really poor synergy with AD itemization.
items like
all enhancing Katarina's kit beyond raw damage.
AD does not, as no AD item interacts with AoE magic-damage.
Katarina's play-style also doesn't open up many opportunities to auto-attack. Katarina can't AA while she's using her ultimate or throwing Bouncing Blades, and if she gets resets she's just not auto-attacking at all, as there's no time in a QWERQWER combo.
Which again, raises questions why you'd pursue AD over AP.
Katarina also lacks AA steroids of any kind.
That's not normal: over 50% of the champions in LoL have something in their kit to make auto-attacks hurt more than what their bases provide. Janna has a +50 AD buff, Sona has an in-built Sheen effect, Akali deals on-hit magic damage, Fizz deals on-hit magic damage, Malzahar applies 100% of his AD to voidlings, Orianna has on-hit magic damage.
Katarina just has baseline AA damage with melee attacks, putting her AA potential at Karthus levels of "why am I using these?".
Granted: it's worth noting AD+tank itemization is pretty solid right now, Katarina's bases don't suck and she's rushed Warmog's in the past, and mixed-damage with potent phys attacks and solid base magic damage isn't terrible.
I just don't see more AD ratios on Kat changing much about her, if anything.