This gif from wikis explains piling pretty well:

Woulda been valid a few years ago. But now the assumption you hit 1's with no food stock in the equation is misleading. Since you can hit 330+ a sniper can down someone where before he would've been only a nuisance.
actually I think it's pretty accurate of RS3 today. In the gif they are hitting the equivalent of a 200 every hit because they only have 5hp there. 200 is probably close to the average hit when you factor in misses so I personally don't see that gif as out of date at all.
Not trying to be obnoxious here but let me clarify: it would have been next to impossible to KO someone if you sniped him back in the day, he'd have to eat up food, but he'd last.
If you snipe today, there's a chance you can down him before he can eat all his food, therefore you gain much more than before by doing it. The .gif is somewhat flawed because the pilers do not stop attacking the pile; if they stop piling and try to hug off the snipers and eat, damage on the pile is also reduced. Even more so if they get ko'd.
I may be wrong, but it's the impression I got from when I got sniped and when I involuntarily sniped in the CP war. I think Lars hit the nail on the head: since I'm not used to the damage you can take from single snipers and since CP are shit like me, it might be effective in a WG v. CP, it's true I don't know about better clans.