I have a feeling the topic kind of moved offtopic a bit. Arty has it's use cases, cav and tanks have their usecases. Depending on how you play you focus on one of both or on a mix. But that's a totally different discussion
To reply on the original discussion "should arty be reduced in power" I disagree. The only thing I'd personally would like to see removed is SnS, But also that is a different discussion. In supremacy the theoretical right use of Arty is behind a line of infantry (or other units) which is exactly how it was done in WWI, huge artillery fire days before the attack between units. Offcourse arty had limited effect on the enemy because they had bunkers to hide in during this barrages.
If you'd want to make it more realistic you should allow trenches and bunkers to be build on infantry locations. and those would be damaged by arty with only limited unit loses... However that would slow down the game heavily, a standing trench was in WWI almost impossible to take without arty covering and smoothing up that trenches defence. However don't forget WWI was a war with months of fighting over several meters of land due to this relation between the high defence of trenches (combined with machine guns) and the rather ineffectiveness of arty against these trench networks. Do we really want to make S1914 more stalemate defence war of attrition wait game? A true realistic WWI game sounds a bit boring.
Arty had it'smain use in destroying fortifications, because the arty in these didn't reach far enough to fight the offensive arty, they were outdated but without arty to destroy those fortresses they'd be rather impossible to take. That was the original use of arty not killing units indeed but destroying the defense of these units. Reducing their effectivness without giving them their use against other defences (e.g. trenches) would render them rather useless or only usefull against city forts and upgrades. But implementing that realistic relation would make the game slower paced to my opinion so not more fun either.