Yeah, you probably won't be very good at assassinating mid game if you shoot yourself in the foot with a zhonya's rush. Vs zed it's good, vs most mages you'll be hosed.
DFG doesn't have to be your first item (though surviving the lane is more about pots, wards, dorans shield, and jungler involvement than the big ticket item you get at 15 minutes), the point is that it's core. Like all reset champs, the ability to gib a specific champion at the start is incredibly valuable to kat.
Malzahar's Malefic Visions Pentakill in King Poro ARAM
Be Zilean support in top lane
the one i'm supposed to "support" rushes like crazy
this person is about to die
use ulti to save his sorry ass
dies 10 seconds later
"Y U NO ULTI ME?!"
I hate players of LoL sometimes
DFG is core?
I'm not saying DFG is a bad item, what I'm saying is that Katarina benefits way more from Zhonya and you shouldn't build it unless you're extremely ahead.
DFG is core?
Excuse me? Most of the main Katarina players don't even build DFG on Kata