The 25 pounders "offmap onmap" strike from Artillery Regiment used to be good in the spammable way, it still couldn't hit the sector you aimed it at, but at least it shot full 6 per howi barrage and was cheap enough to make other arty pieces stay on guard, it wasn't counter, but it was a psyholgical pressure on the opponent being under frequent barrage.
Now that its 100 muni and just 4 shots per howi its utter garbage.
And sexton being oversized mortar on threads isn't an answer for anything 
Yeah its just not viable at 100 muni a pop. And even then it's only "meh" with airburst shells from Anvil. I wouldn't be surprised if Relic nerfed the ability to fire into the FoW because it was "unfair".
I'd be fine with indirect fire spam being a thing against Brits IF a natural counter like Royal Arty was actually viable against it..