Hum I agree with almost everything, but you shouldnt just dismiss the potential of the 2nd brush that has a bubble has main defence ability. Yeah its not ideal to multykill, but doesn't mean it sucks, u know?
That brush is.more of a tactical play nature, assuming you will know the paths and predict ur enemys.movmments and lay mines and keep pressure like u said in the 1st map skate park, leave a mine in the top and flick from.above is far more usefull then charging inkstrike cause when u do so u will.stop swinging ink, and thats when u will likely be killed and the bubble can save u from it and Still allow u to keepp unleashing ink when you shouldn't even be able to(During a Inkstrike 4exmp) also wih this brush u can effectivly fight Kraken users!!!!
There lots of maps where i find her more usefull then others, like that port makarel where u said we "suck" there, but actually we can turn ties easly with a well placed mine or make a swift ambush jutst arround thr conner by sprinting ZR and get behindthem without trouble. But overall, its a nice build.
Ps:4stars not 5, becouse u didnt consider other inkbrushs usefullness