Please CG remove leviathan from the game...

I haven't experienced any bug with Mark VI not executing with the correct number of stacks. You should report that on the Bugs site. Were you trying to insta-kill another Mark VI? I don't think it works on them. I also wouldn't recommend using Tie Interceptor, I'm not sure that its part of any mirror strategy/counter, unless I'm missing something. I don't use it with Levi, so I'm not aware of any bug or weird interactions there. As others have said, in the beginning it was rocky, but after awhile using Levi, I generally don't lose against other Levis, no matter the lineup or who goes 1st. Just makes it harder/easier depending on turn order. What opening lineup are you using and are your opponents using?