Let's compare it with other "similar" units:
MP/Fuel
Speed/Size/Armor/ReArmor/HP
Penetration/Damage/Range/RoF
Puma:
80.0 270.0 or 70.0 320.0 (OH/OKW)
7.2 18.0 25.0 12.5 400.0
160.0/120.0/80.0 120 50 4.1
Note: LMG42 damage, aimed shot (can also be used on
infantry snipers) and smoke.
M10:
80.0 270.0
7.0 22.0 120.0 57.5 560.0
180.0/160.0/140.0 160 50 5.85
Note: Amazing crush, AP shells and blitz
Stug-G
90.0 280.0
6.0 20.0 140.0 70.0 560.0
200.0/185.0/170.0 160 50 5.3
Note: some AI with MGs, Amazing/OP TWP
Su-76
75.0 280
6.3 20.0 70.0 35.0 400.0
200.0/190.0/180.0 120 60 3.4
Note: Barrage and fix turret
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All in all:
-Puma could be slightly cheaper (5f for OH - 20mp for OKW)
-M10 could be slightly more expensive (10-20mp)
-Stug is fine but i'll rather see TWP for it working more like Aimed shot.
-Su76 could increase cooldown on Barrage. Could up by 5fuel.
-I don't think that either increasing the range for the Stug or decreasing it for the Su76 is the solution. Buffing the range on the Stug will bring a huge disparity with the Su85 (for cost) and bringing it down on the Su76 will make it too vulnerable IMO (gun traverse sucks).
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For a lot of people it's not that the SU-76 is "2OP relic pls nerf ;_; " it's that the SU-76 has replaced the SU-85 and made going T4 outside of wanting to get kats or you went an 85 doctrine a risky sell.
It's just to efficient for it's cost. Yeah in 1v1's you can't spam it (although you can get a decent number of them) but holy fuck in 2v2 lately it's just been never ending 76's into ISU or IS2 or god help me howitzers.
You can make it less spammable or make other options more attractive without making it useless. I mean the StuG III ain't got 60 range totally lost it's AI performance and people think it's the bees knees.
1-Su85 can spot for itself, turret has some rotation, 160 damage and 240more hp. Vet2 or vet3 is way better than the Su76.
Going for either is a matter of wether you could tech T4 or not. I still think that Su85 needs a better vet1 ability and that could mean all the difference between both units.
2-No one was building Stugs before for it's AI, they died easily and weren't reliable against armor.