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.
Makoa's Dredge anchor will ignore Reversal entirely so you cannot rely on it. You can, however, hide behind walls and geometry and peek to perform one shot at a time, forcing Makoa to eventually retreat due to poke damage.