I DONT think that Arty is even a bit off the target, its just right as it is now. You cannot call in Artillery if your frontline is melting, so those units are second priority, if you need a tank to save the day. So, you dont have the money for Artillery and other units, too, and if those would be even more expensive, I could not play other units anymore.
Those pieces tax your economy a LOT imo, even if its just 60$ for a nebelwerfer. I must be careful to spend money on those because I am afraid of lacking something more important.
Artillery Observers need to be cheap enough to play without loosing your frontline in the 1-2 minutes you need to hold your front to be able to afford them, because they dont defend your frontline, so you can only use them if you are already save. The range of them is also not very high so you have indeed not a calm day to bring them into range. Its just outside tank range, so you must be careful not to loose them, I need the 'last' existing bocage before the tank comes into range to target the bulk properly. Without the backup you are quite lost with an Observer, because as soon as the enemy comes into movement towards you, its all over, you dont make good targets and lost your money.
Especially in Phase A, an Observer is difficult to bring in, you need to be very good with your other units to make up for the missing defense on your frontline.
After phase A, BOTH players have the possibility to arty down each other, with as many rocket launchers as they wish, even 20 would be okay, because you can stun each others rocket launchers, too.
After the frontline is static, there is nothing better than a good artillery, and I find the arty battles very exciting, very different to wargame, where you never had a chance to hit them properly, it was really a cat and mouse play, that could be improved, sometimes you were lucky, but it was a lot of work to hit arty with yours.
So if you dont get further with tanks and infantry, supporting up with arty makes a REALLY good game for me, because you are not lost into paintballing each other, but you can actually hurt the frontline very fast, bringing things into movement again, and help your tanks to move forward again. You do not stay in the arty state for long time, because the other units come into play again.
Your many Nebelwerfers will be pretty useless if you run out of front troop e.g. infantry. The weakness you get then despite having artillery is so big that you cannot defend yourself, if you go big on arty, especially rocket arty, but expose AT or AA capability. If both players have forces in front of their artillery, the better artillery commander can shaken the pinch of your forces, whereas the other player might have stunned my arty, but cannot stop all my tanks from approaching.
It is really a matter of how you play whether you loose or win against artillery, you have the same strength, mortars and howizers are equally strong, a rocket artillery player cannot ignore and laugh about them. Taking out each other makes a heck full of fun and the arty play is really not boring or lengthy, but you instantly get the flow running again, it is really fun to play with.
And whether its 1v1 or 4v4 or 10v10, you just knock out each other massively like the village people in Asterix and Obelix, you throw yourself into the turmoil and dont want to miss it.
And again: you really must be careful not to risk your frontline to be able to call in artillery. The game can punish you a LOT if you are too confident in calling them. If the price is too high, you cannot recover from a mistake or 2 if you need arty as a counter to turn the key tide. Especially if you are in a weak position.
AFTER the game is once in imbalance, one player has 10 artillery pieces and you have none and also no tanks AND no Aircraft, its all over and out. But that does not happen that easily. You stand on a solid position for very long, you have your own tools to counter that, you are not defenseless. MANY things must go wrong to loose a frontline (you loose a unit or 2, but the enemy does just as easily as you). And then not to unfair reasons. (See the post of the last page. It really connects!) You only get the loss if you REALLY deserved it!
... And I keep editing and finding important things: If you make arty more expensive, you just make the stronger player stronger, and the weaker player weaker, because only the stronger player can afford those then only.