The most toxic part of Katarina's kit...
is not her ult (you can interrupt it)
it's the fact that she's RESOURCELESS with a 675 ranged poke and 700 ranged gap closer.
Just to get an idea, the only targeted non-ultimate ability with a range higher than that is Fiddlestick's E. That's it. Having 675 range poke on a mid-laner means that against mana-based champions, she can easily outpoke you. Yes, initially she will get outpoked when she is facing someone like Annie, but that's not factoring in the fact that she likely bought 4 potions at the start and by the time you're at 10% of your total mana pool, she has healed back to 50-80% of her HP and she'll be able to all in you without you being able to retaliate because you're OOM.
Look at Akali's Q in comparison. 75 less range and it deals less damage. That's not to say Akali isn't toxic (she has a very toxic kit).
Personally I think Katarina should at least use some resource. They're free to cast, with a too short of a cooldown. Most lane opponents you can retaliate them by waiting till they're OOM. You can't do the same thing with Kat, and on top of that, she has amazing targeted poke.
This also makes her too safe of a laner as well. Most champions will have to expand mana in order to clear without using autoattacks. Kat can just freely Q minions with impunity.
