Large Artillery and Explosives are extremely (unrealistically) strong in the game and are, in many cases, not utilized by players due to this.
The Artillery Rounds all have a huge damage radius (in case of the 155mm shell, every human who has no bodyarmor within 120m radius of impact is immediately dead).
The Range itself at which units can get killed or damaged is plausible. But it's unrealistic to have a 100% guaranteed hit or death over the entire lethal area. This makes artillery mass killers. Pushing through artillery bombardment (think of WW2 or WW1 scenario for example) is impossible, as every round kills or at the very least damages everything within it's radius.
Not sure about today, but in WW2 the "lethal area" of a round was usually considered the area where you had a chance of at least 1% or so of beeing incapacitated by fragments. So that means in a large area of the "lethal area" you actually had a decend chance of surviving. According to documents a 81mm Mortar had a lethal radius of 16-19m. The Arma 3 81mm has an indirectHitRange of 18m, but (due to the indirect Damage mechanic) kills all unarmored humans within 63m radius (=100% kill area of 12500m²) !!!
The solution for this is, that a propability modifier should be included into the damage formula. The real damage from artillery comes from fragments. The further out you go from impact point, the fewer fragments there are in a certain area -> less chance of getting hit. At short distance from "ground zero", the propability for damage of a unit should be 100%. As the range gets increased, the propability should decrease until it is 0 %. As propability of hits is also targetsize dependant, vehicles/objects could be defined with a sizemodifier in the config, which would affect indirect hit propability. Alternatively the automatic objectsize calculations that are already used in the game (for AI purposes) could be used.
It's more realistic this way, should have neglegible performance impact, and hopefully leads to more people allowing larger explosive weapons on the servers.