B-4 is an unfair weapon as ISU is. It's not about the ability cost, it's the warning. Stuka dive bomb has warning. At list an audio warning. Your B-4 has zero warning and I just see my expensive fully health Elefant droping to 20% health in one second. Same with the Tiger. This is a balance problem because germans have nothing similar. And you want it in more doctrines. LOL. I would reply to you with a doctrinal german unit that I want in more doctrines, but hey, what do you know, german doctrines have nothing so lethal as B-4.
Have you tried shooting B-4 at something that isn't in the arc?
Unless your army is made out solely from bunkers, there is high chance that none of your units will be in that spot 5 mins later, when it will finally turn.
Also B4 deals 640 damage with direct his. There is 25% chances that your elephant will get a total of ZERO damage on direct hit.
And 640 is hardly an 80% of 1040hp, unless you had a very, very bad math teacher back in the day.
640 is also not 80% of 1280.
You hyperbole so much that its painful to read.