In my opinion cluster ammo are a little bit too powerfull. I have try to partialy solve that :
change value : HE penetration to 4 for 155mm arty
AP penetration = 222 (heat code for the old sub munition)
AP kill 6
Heat penetration 6
For the arty using EFP sub munition (like the "BONUS" shell):
HE penetration =4
AP penetration = 13
AP kill = 1
HEAT : 0
With this value cluster remain devastating against hold APC (BTR 50/60, M113 or pre 1970 tanks) but moderne MBT suffer just a lot of suppression, some immobilisation or kill if you have a lucky top hit.
Many moderne army have start to remove cluster ammo for political, moral (
) reasons but in reality it's becauses this hold weapons systems are uneffective against modern vehicle and too dangerous for fighting agains guerilla or urban area (close quarter fight, civilians, unexploded ammo, ...)