It will heal whatever the BotBase places in the Heal Targeting list to. If you are using a BotBase that does not implement encounter specific strategy/logic, then you can use a mouseover keybind to set the Focus frame to that unit and Singular will include it in the heal list. -Bobby53
I always use Enyo as a botbase, so that stays the same no matter what cc I am using. Using enyo with oracle, it heals the bubble. Using enyo with singular it doesnt.