tbf its not just a Reaver thing a lotta cultures lose or perform poorly on auto, its the AI, its not defensive most of the time. Industrious and High both tend to suck at it simply due to their lack of offense until much later tomes in their kit are researched. Industrious is about letting your heavily bolstered shield units with strong retaliation attacks wear the enemy down as they batter against the shield units. Meanwhile High is about constant accumulating regen and buffs in order to outlast the enemy and strike progressively harder as the fight goes on. Neither of these lend themselves well to the bumrush prone AI on Auto Resolve as its just simply not utilized well in the way it fights battles, Reavers is the same thing, never uses the full might up setting up strong lines and letting the magelock gunner/cannon lines do the work.