Hi there,
First: There's basically nothing wrong with the design decision to have snipers use arty strikes, BUT:
I just want to bring to your attention that the sniper Artillery comes down after 1 seconds, making dodging this ability impossible if several snipers use this skill at once on the same spot, killing everything at this position.
Mg's, mortars, infantry - everything.
I'm sure the reason for the first shell hitting that early is because it is the Forward Observed Artillery Strike from the British officers.
Solution: replace this skill by another arty barrage type, like commando arty. It's similar in power, but that the first shell arrives after 3 seconds instead. In the current state it's broken IMO, cause 2 snipers can instagib multiple squads with the first shells (-> arty strike on the same area).
To reproduce this, just build a sniper squad, then research the Artillery spot upgrade and use it on an area.