Mauga has sustain issues regardless of Ana. Too much of his sustain is based upon hitting things which is only high and consistent on hitting larger targets.
Its quite the oversight from Blizzard to give say a Sigma high sustain for literally doing nothing (shield or grasp) along with many other tanks (shout, shields, defense matrix, etc) while Mauga instead has to be always vulnerable and needs to lands a crazy minigame of land 10shots for fire, then land more shots for paltry sustain on non-tank targets.
That felt fair when he did like 90 DPS with up to 180 DPS on the crit fire, but with the reduced damage and 15shots and 72 DPS small targets straight up hard counter Mauga. At least with Roadhog you have hook to deal with them and if you miss you can heal up on breather.
They made Mauga way too tank focused and didn’t make him more balanced by say shooting at other squishies is actually a viable form of gameplay. The guy needs some form of stable sustain such as letting him gain shields on simply firing period and rewarding more shields for things you hit. Let him gain +1shield per bullet fired and +1 more for hitting something be it shields or other players.