currently the Rift Torrent augment gives damage for every enemy affected by rift surge, this damage is reduced every time you kill an enemy.
it would greatly benefit limbo if instead of that, it snapshotted the damage bonus on the initial cast and reset it when ALL enemies affected by that cast are killed and additionally on the next cast of the ability.
so if limbo casts rift surge on 5 enemies and gets 200% damage bonus, that damage bonus does not decay with each kill. if 1 of those enemies is still alive when limbo casts the ability again and only gets 3 enemies, he loses the 200% damage bonus anyway and gets the new 120% damage bonus, even if that last enemy from the previous cast is still alive.