So far, it hasn't really been an issue for me. I don't like the lesser damage of the HE only firing, then again, I never used Premium on SPGs, just felt dirty about it. That said, I think buffing the damage an HE shell can do and maybe buffing it's penetration for under 100m isn't awful as an idea. If they changed the alpha of the rounds, I would think increasing it by 30% would be in order. They were reduced by Half, which means this increase would still place them at about 2/3 to 3/5 original values. Let me see, real quick.
Let's say you had a shell that had an alpha Pre-9.18 of 300. Now it has 150. If you were to increase that by 30% of now, you'd have 195 Alpha instead of the original 300.
If you did that and maybe removed the stun effect or considered reducing it by 50%, I'd be okay with that. I'd honestly be okay if stun didn't exist. The changes to accuracy and reload do not more than compensate for the other nerfs, not by any stretch, however, I have come to believe that many of the higher tier arty is the real issue.
Maybe what WG should have done was tie LTs to SPGs in tier levels. Thus, until recently with 9.18 and tier 10 LTs, there should have been none until the change and no Spgs that were above tier of the LTs they are supposed to be operating with as fire control. I came too late to the game to offer this wise and obvious manner of 'fitting' arty into the framework.
All that I have read and my personal experiences is that, post tier 6, arty becomes just too devastating due to that extremely high alpha damage, so the reduction seems mechanically and balance-wise necessary. I think the pen levels might have been increased just a tad, too, though I don't think so, really. A couple mm of pen (the difference between 23mm and 28mm is not much of an increase at tier 6, especially after halving the alpha of the round) is not sufficient to make a serious contention of 'buffing' the HE rounds' penetration.
The stun, though. As a receiver of it, I haven't been that much inconvenienced by it. I can still move, so perma-stunning comes in when you are caught in a bad spot. That happened before the changes and ended up with a dead tank nearly immediately. I still don't think the stun mechanic makes the game more fun or challenging in any way. So I'd be okay with dumping it completely. In the alternative, maybe the stun effect could be reduced a bit if it can't be eliminated.
I admit, I pretty much like playing arty. I don't like it as much as playing Mediums, Heavys and TDs; though with my bad connection, it leaves me little choice. Most times, with my frame rates and ping, it would be hampering my team on purpose with a front line unit. I still want to play, though, so I play arty more than I really want to, just to be able to play.
GL, HF & HSYBF