There are a lot of things that could have been done differently here, but here are a few of my most immediate suggestions:
* Don't defend with axes. They cost much more than warriors, but if you lack Iron they aren't much better on the defense. You should have sent a large pile of them against Iskender early on, not sat them around waiting to get murdered by collateral.
* Use every advantage you have. Not attacking with the Sons was a terrible and obvious mistake. They also should have been more proactive in defending cities, stacks and themselves with Elementals.
* Don't wait for Ogres. They're strong, but you already had numbers and the power of the Sons. As Iskender has demonstrated, even base strength 5 units are easily sufficient to wipe out an empire, as long as you have collateral. Ritualists and axes with shaman support would have been plenty for you.
* If your opponent is relying on tiger spam to fill out their military, build lizardmen. Not only do they get great odds vs. tigers defending, but if you had used a couple "capture animal" promoted lizards you could have turned his own spam against him.
* Don't defend with axes. They cost much more than warriors, but if you lack Iron they aren't much better on the defense. You should have sent a large pile of them against Iskender early on, not sat them around waiting to get murdered by collateral.
* Use every advantage you have. Not attacking with the Sons was a terrible and obvious mistake. They also should have been more proactive in defending cities, stacks and themselves with Elementals.
* Don't wait for Ogres. They're strong, but you already had numbers and the power of the Sons. As Iskender has demonstrated, even base strength 5 units are easily sufficient to wipe out an empire, as long as you have collateral. Ritualists and axes with shaman support would have been plenty for you.
* If your opponent is relying on tiger spam to fill out their military, build lizardmen. Not only do they get great odds vs. tigers defending, but if you had used a couple "capture animal" promoted lizards you could have turned his own spam against him.