Though they are adaptable and can fit at any terrain, Amazons have some unique weaknesses owing to their faction abilities.
Their strongest ability - Javelin/Kukri Charge - essentially costs two maneuvers and a minor terrain, which means it can be tough to get lined up just right. Mages can offset this slightly by recovering buried minor terrains, but in any case they require minor terrain to access their most potent faction ability.
As their mages lack any element, they lose out on a lot of spells while hiding in Reserves. Their abilities still function, but the best Reserves magic - things like Fiery Weapon and Wind Walk - require bringing magic equipment to access in Reserves.
Their faction-specific spells can be somewhat lackluster compared to other factions. Rally can be useful in the right scenario, and Esfah's Gift can get extra mileage from minor terrain, but they don't compare very well to other faction spells like Tidal Wave, Wilding, or Necromantic Wave.
Amazons are generally low on saves naturally, so they can be fragile to counterattacks without defensive measures in place.