You want to show splatters on
your screen
as any member of the group is low at health?
Makes no sense imo as you first would need to check which of the group members is low to turn to it and us the front conal heals or get in it's heal range.
I'm also using Unit Frames Rebirth and it is great. You always have to check the group members and the enemies attacks if you are a healer so looking at the frames and the gameplay will automatically show you who is low or will get low soon and you are prepared to heal the correct ones fast then, instead of keeping your head down and start searching them as they are low already (which might be too late
).