Sorcery is among mediocre secondary skills. The fact is that creatures cause significant part of the damage during combat, and enhancing spells like Bless can easily cause more damage than most of the spells causing damage. Perhaps the only exceptions are Armageddon and Implosion. In other words, it is more lucrative to spend the combat round's spell to enhance the troops than to cause damage to enemy creatures. The consequence is that Air, Fire, Earth and Water Magic secondary skills - that similarly enhance the effect of spells - become more preferable than Sorcery.