One of the key things that made kat viable mid was her relatively reliable RANGED harass with Q buffed with killer instinct. Kat really needed this advantage over other ap carries because she would lose to almost any ap mid in 1-for-1 nuke trades if she got into range to Q-target the enemy mid directly and would put herself into an even worse position if she Shunpo'ed onto the enemy mid.
Bringing me to my next point:
Killer insticts was a LOT more important than the general public or even riot gives it credit for. Not only did it give Katarina some relevance in the laning phase, but it also was a really GREAT aspect of kat that experienced kat players could abuse. For example, you could activate Killer Instincts 10 seconds prior to an engagement and then have it right back up a couple seconds after using Q or E.
Now, the only way kat can get in some significant damage in the lane is if she gets in melee range. This is contingent on two conditions that must be true:
1. kat won't be instagibbed or out-traded by the enemy ap mid as a result of entering melee range
2. enemy jungler is spotted somewhere on the map
By removing her Killer Instincts, you are effectively nerfing Kat's early-mid game considerably, forcing Kat players to take unnecessary risks if they have any hopes of winning their lane.
Now, virtually the only way kat players can get kills at mid is if (a) the enemy ap is a complete imbecile or (b) your jungler ganks your lane successfully.
Not to mention, by implementing this kat remake, you are just turning her into an akali clone. Q applying marks? mark being consumed by basic attack or ability? W small aoe spell? is this a joke? In your constant efforts to make every champion unique, I was confounded by your decision to implement these changes.
Furthermore, you say in the youtube riotgamesinc mid-august patch preview video that kat's ultimate is unreliable? This is simply not true. As a kat player, you simply have to time when it is appropriate in any given teamfight or skirmish to use your ult (after the relevant CC has been burned) there is no real need to make any changes to her ult.
I sincerely hope that you consider retracting your kat remake decisions. Kat was an amazingly fun and viable champion to play, if played right. I honestly do not understand why you decided to remake this champion.