These are both things that we have experimented with giving them higher stats on, but it hasn't felt right. For instance, if we look at Battleships bombarding units on the coast, they tended to bombard them for short periods of time (in game terms) and not always with the expected effect. But in game if they have good stats and naval/aerial superiority, a player might use their ships to endlessly bombard enemy units for months or years on end... and this itself wouldn't feel right either.
As it is, both unit types can to varying degrees be used to soften up a defender because they will both demoralize the defender by 20% per attack, while artillery will also de-entrench them, which is very useful if it is the first thing done to a targeted unit. The difference between the artillery de-entrenching the target and another unit doing so, is that the artillery will do so without receiving any losses, which makes it a cheaper victory when your land forces do go into the attack.
Artillery units in game for the most part represent specific concentrations of Heavy Artillery, and are in addition to the organic artillery present within Corps, Armies etc. So their presence in game is as an extra, but if made too powerful they don't feel right, so it's all a question of balance.
That said, upgraded artillery do have better stats which give them attack values of 1 against ground units. With this, they will start to inflict more losses too.
Plus they can be useful in defence in disrupting an attack due to their ability to provide Defensive Fire. Perhaps they're not a priority unit, but I certainly find them useful at times.
< Message edited by Bill Runacre -- 1/7/2018 7:24:35 PM >