Glad that can help.
I did not mention a few "classics" among others.
The 20 AI Titans shoot the poor troop with just one Gargoyle.
Or the 30 Phoenixes attack the poor troop of only one Archer.
During a siege, the human player positions one of his troops right next to the entrance to the castle.
The AI advances one of its troops and opens the drawbridge to attack the opposing troop.
The AI troop is eliminated by the retaliation of the opposing troop and the castle door is wide open to let the opposing troops enter.
The AI casts a Summon Elemental spell several times when once would have been enough to annihilate the entire opposing army.
The AI casts Summon Elemental spells and also sends its regular troops into combat and thus loses creatures from its regular troops when it could have sent only Elementals in contact with enemy troops to annihilate them, and thus having no loss in its regular troops.
The AI casts a Summon Fire Elemental spell.
The human player uses the Cold Ray spell (double damage on Fire Elementals) on the Fire Elemental troop and reduces the troop to just a few units.
Despite this, the AI continues to waste his magic points casting Summon Fire Elemental spells when it's ineffective.
The AI could have cast other much more useful spells in this case.
Some tactics the AI could use.
During a siege, if it is to its advantage, the AI could position one of its troops just in front of the entrance to the castle thus preventing the opening of the drawbridge.
Defense troops can thus be decimated with spells and ranged attacks and be reduced before melee combat.
This is a tactic I use when I have a lot of ranged attackers in my ranks and not a lot of melee troops to defend them and I'm attacking a castle with a lot of melee troops defending.
Sometimes it can be advantageous not to eliminate the slowest troop when it is part of the opposing army.
This ensures that you get the hand first in the next round.