Ever since WG change how SPG works it became worst in my honest opinion. In the past you'll get one shot by arty if you are open, so what do you learn from that? Don't stay in the open, if you get hit its a training punishment, to that end player become more aware and constantly stay in cover. Once the change happen no matter what cover as long as the splash close enough its a performance penalty + high tracking chance, from then on if there is more arty in that match you'll just be permanently track.
This also create an issue where heavy tanks that is slow just camp like TD way behind the line because they are too afraid and not willing to take the risk of getting spotted. End up you have a bunch of genius just holding in "safe zone" and turtle as long as they can and hope others brave enough to open a line of opportunity. Many times you see match where one side send a kamikaze tank especially the hill climbing map, all he need is to spot the heavies then spg focus fire and now all the team is so afraid to go up kill they just run back down to camp in the forest. This kind of game isn't fun, its basically just boils down to who knew such tactic from the start, especially for scout. Sure there are many other ways and strategy besides going up the hill, but if your game basic mechanic force the majority to react with the intention to survive by just camping it has defeat the purpose of the game main and basic objective, which is battle and engagement. Why display the pride of a tank when all the game is forced to camp and wait not because it was a strategy but because of arty?
Ask any regular players, what is their thinking process when there is arty in a match, they would tell you if there is one they take a little risk moving from cover to cover, 2 arty they stay in big cover position early, 3 arty .... base camp, too risky to even cover 20% of the map. In the past arty reloading time is slow, giving time for heavy tank to repair and take cover if they did not get 1 shotted. Now arty reload time is so fast you can basically lock important tank till death, I did it a lot of times on my FV304 by waiting my teammate to fire a shot and track heavy tank, then I fire my first shot follow up just roughly 1 - 2 seconds apart and sure enough enemy used up his repair kit just to get track again by me and there is no way or chance to ever move again, not unless they wait past the refresh from repair kit.
From my perspective the spg change from WG is purely money motivated, they make arty their puppet to track players and with the fast reload speed threaten any that doesn't auto repair track to move to die on the spot, there is no different if you get one shot or pecked to death, the mechanic is design to force you to dap the repair key without even thinking, unlike the past when you get hit by arty you still could decide if you want to use your repair kit or not depending on your situation. The change was never sincere in solving the issue of the past, its just made so things move faster or more. They are also crunching out thicker and thicker armored premium tanks to make using AP rounds at the brink of usless but thats another topic for another day.
Right now SPG is just a mindless play, you find starting spot (usually around your base) and most of the time for the rest of the game you just sit there and wait for spotters to light up some target and fire away, with only 1 type of shell you don't have to think about your load out, you don't have to think in a SPG tank anymore because your reloading time is much faster and you can just spam in lighted area. The purpose and role of a spg had become a point and click, look at map, see things light up, spam away.
Now if WG is sincere in hearing opinions out here is a free suggestion to consider.
-Give SPG AP and HE round
AP - with AP round the accuracy is better, decent pen (base on their own tier) so its like a long range sky shell, dmg reduce to low the purpose of this is to take shots at exposed enemies.
HE - with HE the accuracy is less compare to AP, low pen ..... when hit enemy can track, but the area that it hits create a small patch of dust cloud, enemy is hidden within that cloud for a short time. The purpose of this is to hold enemy in position.
This would change how boring SPG was to a more interesting perspective. My explanation may be too brief, so I'll demonstrate with an example.
Lets say I'm running with my FV304, I go to a hidden position, enemy spotted, I decide to use HE shells, hit enemy, teammate blind shot into the cloud, hit some miss some. cloud effect over enemy back up came, fire another HE shell, this time in the middle of the field, you still see both side light up on map, just that in 3rd person or fps mode you can't see enemy outline, you can maybe see rough tank shadow. The HE shell would be a double edge sword function, you shell enemy to track them ,a chance for your enemy to decide if they want to repair to back up or take a chance at cross fire with what is in front of him. Second function is to smoke screen your own teammate position, useful when trying to move to risky place and need some arty cover to help, in this position arty is not just only all about spamming on exposed enemy, it has now had another purpose and function, which is provide smoke screen for your own ally to move or push. It can also be a decoy to hox enemy into thinking that because there is a smoke screen therefore some enemy tank must be there, trick enemy into spending shells on non target positions. 3rd function is same as what normal HE do, splash and injure crew etc.
Now both side on heavy fire, as a spg I wanna help teammate do some dmg, so I switch AP round, 110 pen 75 dmg 15 sec reload time, in this case I can pump some dmg to help fight against weaker tanks, forcing them to relocate I can also sort of defend my self if enemy get close if I choose AP over HE. With AP maybe you have shorter effective range compare to HE.
The idea is roughly in that sense, the adjustment can be made base on their own preference. The purpose is to adjust SPG to still be playing the same role but in a more active way, The advantage of spg all this while its the tank's ability at long range engagement, but should never be a couch potato tank.