those soft targets you mention have 320 hp, so they'll still need 2 shots to kill even with 200 dmg per shot (or 240, like the kv-2). same for mediums with 640 hp, which will also still need 4 shots to kill after your redesign. and with a concurrent rof increase to balance out the net dps gain against other targets, you're suddenly looking at an even less powerful is-2 against the targets you mentioned than before.
hardly worth it in my book...
In a vacuum 200 damage would mean a whole lot, but the soviet have a some "sub standard" AT that it would make a difference for. A wham bam with a su76 and an IS-2 would be half a p4s health for example, or in conjunction with PTRS' you cound find some ttk shaved. Half the stock AT the soviet have would see a difference.
Plus, even though it's only 40 more damage, you notice when a firefly hits you. It would do a bit to make the tank FEEL more powerful, even if ttk itself is wholey unchanged.
Right now the is 2 is a good tanks, a reliable tank, but not an interesting tank. And since it's only in 2 commanders the lack of interesting sort of waters down the draw of those commanders. At least for me.
Again, it's not necessary. But it would be nice