1. Fuel tanks absorb all spall but don’t produce any.
Russian tanks have a very nasty habit of stopping all spall after being penetrated. Meanwhile NATO tanks’ fuel tanks produce enough spall to kill 3 or more crew members. Is this incorrectly modeled? Well, no. See NATO tanks such as the Abrams for example have firewalls for internal fuel tanks. In real life these would help to protect crew against potential fires, however in war thunder they do nothing but produce massive amounts of spall despite only being around 20mm thick in the case of the Abrams. Additionally, fighting compartment fires in war thunder are not nearly as lethal as they should be. Since Russian tanks have no firewalls for their fuel tanks, they would likely rupture, spreading the likely ignited fuels all over the interior of the tank. To recap:
-NATO tanks suffer exaggerated consequences of fuel tank firewalls but none of the benefits
-Russian tanks are too survivable after a fire in the crew compartment
2. T-series tanks are too survivable.
Gaijin has modeled tanks like the T-72/T-80/T-90 in such a way that makes them very compartmentalized and resistant to spall. The biggest offender is the carousel autoloader found in these tanks. The auto loader helps to stop spall from reaching the crew our ammo. And after eating spall, the autoloader is often only mildly damaged. Furthermore, the autoloader produced almost no spall after being hit, further adding to this issue.
3. NATO tanks have overly fragile turret baskets models and T-series do not.
This is a bit more of an Abrams/Leo 2 cope problem than anything, but it’s still relevant. NATO tanks (especially the Abrmas and Leo 2) will often have weapon drives, turret baskets, hydraulic pump, and power electronics all modeled in addition to the actual turret ring. What do Russian tanks have? Just the turret ring.
Also, a bit unrelated but Abrams/Leo 2 having their turret baskets and hydraulic pump/power electronics modeled, but no other tank having it is total bullshit and gaijins way of artificially nerfing these vehicles.
4. T-series tanks have smaller, less lethal weak spots.
To be fair this does kind of just come down to tank design, but it is undeniable that NATO weak spots are much less survivable than Russian ones. Take the LFP on a T-72/T-80/T-90, shoot it and more often than not you will kill the driver, autoloader, and the engine. Problem is that they can now shoot back. If you shoot the LFP on the Abrams for example, with a shell as weak as DM33, you kill the driver, gunner, turret ring, engine, and severely injure or kill the commander and loader. The same is true for the driver’s port on a T-series tank, which mind you gets drastically more protection on the T-80 and T-90. You get the driver and after that is typically about 50/50 whether or not you kill a crew member in the turret. Shoot the turret ring on the Abrams and you kill everybody in the turret.
5. Addressing the terminator in the room.
Now most of these problems are with the hull and get reduced as you face more powerful rounds at higher BRs that produce a shitload of spall and just don’t care. Now imagine if you took the hull of a T-90M, the best Russian tank, slapped 2 BMP-2 guns that can fire APDS or anti air rounds, and also gave it ATGMs with 800mm of pen… and then you put it at 10.3.
To put into perspective how insane this is, another vehicle built on the hull of a top tier MBT with an autocannon and missiles is the NAMER, and that sits 11.3. A full BR higher. Yes I know it’s not apples to apples since it gets better APFSDS rounds and FF missiles, but still.