USE YOUR WALL! It blocks fatal attacks, (Terminus ult, skye ult, ruckus ult, willow seed, BK grumpy, etc...) Most healers need line of sight to heal. block vision from a single target with your wall and burst them down before their healer can react
When Makoa is stunned, aim a bit lower on him to hit his head hitbox. Once you learn the location of his stunned head hitbox you'll see it's very easy to output high damage on him during his being stunned.
When you see him use Billow, wait a little while before transporting away because he cannot cancel the ability and transporting away too early gives him time to close the gap on you.