Are the two shots from the Snap Shot ability on the same game tick?
The animation from soul split is just a visual effect. Soul split returns 10% of damage dealt as health, and it is not tick-based. Here are some pictures:
This is before I casted snapshot (seen on my ability bar with the shortcut A).
And this is after. 3648 damage was dealt in the same tick, and my health increased by 354.
While it's not exactly 10%, it's clear that it's not healing you based off one arrow, but both. So, to answer your question, the two shots from the ability are combined into the one soul that heal the player.