I pretty much followed what I usually do with Skyfallen Gift H but with a bigger emphasis on getting healers out.
I created 2 healing zones with attack units placed before healers. One in the top left corner (Adele, Bashira, Iris), then one in the bottom right (Spica, Chloris, Alissa). I finished it off later with Cyrus and Elizabeth in the top left as the blobby guys make their run towards the top right base.
The blobby guys move around the map a lot going in and out of kill zones so by the time they made their run at the end they were pretty depleted.