Simple geometry. 
I loved Scatter, and I like it more then Storm Arrows. I would like at least have an Experimental Card were it comes back, but with a damage cap at say, maybe 150?( I think thats as much as Ashes TNT, but I don’t know) No more 1 shot, (exept Tracer and baby D.Va, but hey, Tracer shouldn’t get hit by it much, and D.Va is out of mech) and it still completes its job of finishing off targets. And, I do like wall bank shots…
I will always miss scatter, seeing the arrows bounce in a small hallways and decimate the enemy always looked so cool. They could have just reduced it’s damage instead of giving him an arguably even stronger “shoot faster button”. Hell they could have nerfed the ability to garbage tier trash and I’d still use it because it looked so god damn cool.
Alas instead of doing the dreaded thing of balancing the ability (Blizz’s boots are shaking at the mere mention of the word) they just tossed it to the dogs.