@Vaultboy: Use the
Knowledge Database or the Help&Support forums to solve particular bugs. That one has an almost 100% fix with the arrow-code. (UP DOWN etc.) I'm sorry that it's not working out well for you, and I agree LoL is not as stable as it could/should be. On the plus side, it should get far more stable over time :P.
As for Kat, the Killer/Shunpo combo is AWESOME, as you said. I agree that it does not synergize perfectly with her Q. That being said, all the anti-healing skills got a major buff as of late, so perhaps it is better and I just haven't seen it in action.
But yea, Katarina comes up fairly often in high level play where she needs to be tweaked somehow. Not majorly redone like some heroes, just some tweaks here and there.