well... in fact this image dosn't probe "bad balance"
a BW CV on blitz can do quite an OP role on a nowayout 1 map, while a TB CV will face a lot of planes killed by auto AA. today i've just made my personal record: 60k on a blitz with a Ryujo
talking about BBs well... the gunners are almost the difference between a fail ship and a monster ship. I have seen it all. AWhore triple 8' revenge. OP "almost" capped Guam and on the other hand failboats with 8 seconds reload time of a random rain that couldn't hit anything.
a CA it quite more balanced ship than a CV or BB in blitz, you know that you rule almost any lower class, you can face most of the BBs and you have the speed to keep up with BK real fights, of course no CA will be an extremely OP ship, but they do quite nice, a Baltimore, Myoko or County can make something like 30k damage on a decent battle.
Some CL are very hard to kill, like Capitani Romani, others are OP by their mere being, like kitakami. Some DDs are extremely OP, like the Leone, wich its not even fair to have that range and that firepower with that FF1 size. Others like DDX or Z99 are quite decent war machines that can rush and even kill almost every ship in blitz.
so... my point is that you don't need a better balance system on blitz because you can't compare ships by class or even tier. every nation have their great decent and horrible ships, and with that said, there is no comparisson between one ship and another of the same type, due to the big difference that represents EBVE sailors compared to "normal" base12 non boosted with just a few experts and vets