Compared to the Z15 Erich Steinbrinck at 4.0 you get a ship that:
Has the same main calibre (4 12.8 cm guns)
a worse anti-aircraft armament
Slower (66.7 vs 70.3 km/h)
Six torpedoes instead of eight
No depth charges or mortar
So for that 0.7 BR increase you get:
A fuel tank that covers the rear magazine (not the front one)
22 more crew
Mines
None of which is enough to make up that BR difference. It should instead be 4.0 rank 1, replacing K2. K2 can then move to rank 2 and Z32 can move to rank 3.
I’m gonna say it. Skill issue. I don’t really care. As long as I can get Elbing and Emden without researching ANOTHER DAMN DESTROYER (I’m so close to finishing rank II) I’m happy.