To be fair it looks pretty decent, the 'preparation time' or basically charge up for the double shot is an interesting way to do it, I presume you can move during this time so you could charge up and then move round a corner and then fire.
Can it only reload one gun at a time? Thus it's 13s reload for single shot but 26s to reload both guns, plus that 7s block period?
I will say though that IMO the double shot should get an accuracy penalty, make it more like a shotgun for closer ranges, of course in this test tank the accuracy is 0.44 anyway which is pretty bad but I am presuming a tier 9 and 10 will have more like 0.38 accuracy, so should IMO have like 0.44 say for double shot, something like that.
Initial thoughts are I think they have some interesting and potentially balanced here.
Still worried they might IS-3A it though, and make this more idiot proof, because at the moment this is a lot to think about for your average heavy tank bob, charging before a double shot, which mode firing mode to use, what the reload will then be, being careful to give clearance round corners for both guns so you don't fire one into a wall or aiming for spots where both shells will hit.
A lot of skill cap there so the cynic in me says they will make it more idiot proof.