Albowtrosses are recommended if you saw the enemies have lots of tanking units. Fair amount of Albowtrosses with "Blazing Bolts" can really deal much damage to tankers. Although their speed are slow, they are recommended to be used on pressuring the enemy. When encountering an enslaved giant, an allbowtross can move up and down to dodge the rocks the enslaved giants throw.
To protect Albowtrosses, you must have Giant with Giant Growth II to tank the damages except AOE spells. So, try to prevent Albowtrosses to attack lonely. Try to train Giants and Merics to heal them as their speed is too slow to garrison.