tl;dr: lower frustration, increase strategy and maybe add some uniqueness.

Let me start with a joke: Arillery.

Edit:
I want to highlight that 2 of my suggestions are:

different non damaging rounds

and

lower alpha damage and less penetration

Wich should drastically decrease the damage output.

Artillery as strategic support class

This Post is structured in 3 phases: “Handling”, “Effect” and “Distinction”.

Each can be deployed by itself.

Phase 1 “Handling”

These changes reduce the frustration to play against artillery and increase the fun to play the artillery class.

Artillery warning

If shot on, the HUD warns the player for incoming fire, enabling player to dodge shots.

Weapon handling

The handling of the gun and payload needs to change to increase the experience on both sides.

The Fire rate needs to be increased, to account for a lower alpha damage and less penetration. Especially heavy tanks benefit on the receiving end, but the artillery player can take more shots on different targets, or still shot on heavies to harass them.

A slightly increased flight time forces the artillerist to think about their shots, especially in combination with the artillery waring.

Lower alpha damage ~2/3
Lower penetration ~½
Slightly increase payload flight time
Increase rate of fire ~x2-x3
Increase carried ammo to maintain damage potential

Phase 2 “Effect”

To establish the strategic aspect the artillery player can choose between different non damaging rounds. This reduces the potential damage of the artillery, but increases the strategic value of artillery play. The munitions could vary by nation.

HE – Damage, without stun.

Premium – Damage, stun und larger area of effect.

Baric – Stunns crew, damages modules, low penetration, low alpha damage (max 10%).

Smoke – Reduces view range, enhances camo, only triggers positive effects on the own team.

Mines – Area denial, self destructs after ~2 min. Mines are obvious to see and may be destructible.

Target marker – Calls in a light airstrike from a different direction. May vary on nation. Only stun and modul damage, or light damage.

Canister, Airburst, Cluster– Destroys modules in a larger area.

Incendiary – Low power area denial, damages engine and fuel on direct hit.

Illumination – Reduce camo ratings or unveil low camo tanks.

Phase 3 “Distinction”

All artys can activate a siege mode in about 10 seconds and deactivate it in about 3 secondswhich gains them nation specific abilities, but renders them imobile. The following is interchangeable.

Germany

Burst – While in siege mode, the artillery loads the ammo like the Italians and discharges it in one salvo.

Sovjet Union

Undetectable – While in siege mode, the artillery warning and the counter battery detection of France are not triggered .

United States

Indirect fire – While in siege mode, the angle of fire is set to plunging fire, which allows to hit enemies behind cover. Probably loads a little longer and flies a little longer.