While maybe 4.7 is maybe a bit of a stretch, it should definitly not be 4.0, that is far far to low of a BR for its performance. While there suddenly will be more guns that can deal with it if its BR is increased.
As it stands currently at its own BR or even those that at just at the BR below it (3.7), then of tanks that are not Tank Destroyers, there is only really the Pz IV that can to some extend reliably deal with it, in regards to its cannon. If we include tank destroyers, then it is probably not more that a couple of handfull of the total amout of vehicles it can face that can do anything agains it.
That is if it is even possible to aim a weakpoints, because many times they have bushes that cover their turret & hull, so you have to guess of where to aim. At the same time, it also have decently good mobility of that heavily armored tank, and are probably moving, so you have to constantly move your aim for the weakpoint.
If i really have to highlight, of how few tanks that can deal with it, then i would say they need around 140mm pen either AP or APHE, to be able to deal with it reliably.
Currently at the following BR or below this is the amount of all tanks that deal with the KV-1E/B:
BR 3.0, Total tanks: 5
- USA: 0
- DEU: 2
- RUS: 2
- GBR: 1
- JPN: 0
- CHN: 0
- ITA: 0
- FRA: 0
- SWE: 0
BR 3.3, Total tanks: 13
- USA: 1
- DEU: 5
- RUS: 2
- GBR: 2
- JPN: 1
- CHN: 1
- ITA: 0
- FRA: 1
- SWE: 0
BR 3.7, Total tanks: 19
- USA: 1
- DEU: 8
- RUS: 3
- GBR: 2
- JPN: 1
- CHN: 1
- ITA: 2
- FRA: 2
- SWE: 4
BR 4.0, Total tanks: 26
- USA: 1
- DEU:10
- RUS: 3
- GBR: 2
- JPN: 1
- CHN: 1
- ITA: 2
- FRA: 2
- SWE: 4
BR 4.3, Total tanks: 32
- USA: 1
- DEU:13
- RUS: 5
- GBR: 3
- JPN: 1
- CHN: 1
- ITA: 2
- FRA: 2
- SWE: 4
BR 4.7, Total tanks: 44
- USA: 2
- DEU:13
- RUS: 8
- GBR: 5
- JPN: 3
- CHN: 2
- ITA: 5
- FRA: 2
- SWE: 4
BR 5.0, Total tanks: 54
- USA: 4
- DEU:14
- RUS: 9
- GBR: 5
- JPN: 4
- CHN: 3
- ITA: 6
- FRA: 3
- SWE: 6
BR 5.3, Total tanks: 71
- USA: 6
- DEU:18
- RUS: 13
- GBR: 7
- JPN: 4
- CHN: 5
- ITA: 6
- FRA: 4
- SWE: 8
And outside of Germany with their Pz IV (4 of the total for germany), then most of these tanks are not what people would go in as first or even second choice either because they are too low of a BR for people to put into their lineup or for a lot of the Tank Destroyers, they have no turret and are very lightly armored, so most people would not go into close quarters to deal with them to deal with the KV-1E/B. At the same time they would need to take time to aim for weak spots, where the KV-1E/B will just be able to shoot anywhere and be able to kill them.
Probably the best argument for it to go to 4.3, is that is alreay at 4.3 in AB & SB, and for AB people are able to see where and if they can penetrate it, but it is still a higher BR than RB, that just shows how effective the armor is.
And to counter the argument of it only having 88mm pen, and not being able to fight Tiger H1 or M4A3E2. As every Jumbo player loves to say, aim for the MG port, because the 88mm is enough to go through it. In regards to the tiger, it will not be able to deal with it frontally, the only way is if it can get onto the side of it, but if we take onto the flipside of it the Churchill I with 89mm pen, cannot pen the KV-1E/B anywhere, even if it somehow gets it flank. Or taking the 75mm gun that is on the Shermans, with either APHE or its APCR it needs to aim really precise shots on the driver port or very small spots on the turret to go through the front of the tank.
So to sum it up, there is so few tanks in the tech tree at the BR of the KV-1E/B that can actually deal with them, therfore they nearly have no enemies that they need to worry about. And those that can deal with them are either nearly not used and/or easily dealt whit by the KV-1E/B.