Makoa's shots will halven in damage before beginning to fall off at 65 units. Memorize this distance and stay out of it to render him ineffective at damaging.
It is possible to stun him and kill him in ancient rage. So any crowd control ability can pin him allowing you to either move away or let the team focus damage on him.
Shell Shield has the longest base cooldown time of any shielding ability and Makoa lacks a Legendary card that reduces its cooldown. Shoot down the shield when possible to ensure its usefulness is limited.
Never challenge Makoa.
Except when you have Crowd Control ability. ( If he dont have LEVIATHAN legendary card )
Or keep a long distance from him while shooting.