Xerxes the Great...maybe how to make him greater and possible solution for Babylon siege also

By changing it to Crush damage, not only does it no longer benefit from the Blacksmith upgrades, which only affect pierce damage, but both Infantry and Cavalry units have a solid amount of Crush resistance baseline - Cavalry units have .5 Crush Armor baseline (Compared to .42 pierce armor for units without baseline pierce armor), and Infantry have .3 Crush Armor baseline (With only a handful of infantry units having baseline pierce armor)

This is not the buff you think it is, but is instead a significant, massive nerf.

 

Buildings are not an issue for both War Wagon and ESPECIALLY not for Siege Towers, which deal natural crush damage anyway. Both the War Wagon and the Siege Tower have incredibly high pierce armor. Buildings are not going to destroy either of them - The enemy units will. Additionally, War Wagons make quick work out of anything that isn't a Fortress due to their high damage per second, while only taking damage from Fortresses due to their high innate range - More then enough to outrange pretty much all towers.

The plan is - Kill the army. Destroy the production buildings, which is done as soon as you get in range. Once all production buildings are destroyed, you then destroy the nearby forts and towers.

Again, it's not the buff you think it would be. Hell, even just a mere 50% more damage to buildings bonus on Xerxes is more then enough to boost War Wagons up, and again, Siege Towers already deal incredible amounts of damage to buildings once they get up close. Hell, Siege Towers can't even use their range attack on buildings, so it would just be a direct nerf in their case (Though their building dps would shoot up to 2000 damage per second when in melee range - basically one-shot all towers due to how a ram's attack speed works)

As it stands, War Wagons are currently the highest damage output of all Range builds in the game. The issue isn't how fast they take down buildings - It's how slow they are. You waste quite a bit of time just moving the War Wagons from point A to B - Time that the enemy uses to replinish their forces, send out another wave, maybe research another tech, ect. It's why for Egyptians, while Elephant Archers are actually a very strong build in terms of dealing damage (Second strongest), they aren't mainstream because War Elephants can easily get in and destroy all or most of the eco and production, thus making your next wave go far more smooth. It's why Horseman builds for Celts and Norse have gotten nerfed - They were able to get in and smash production/eco far too easily compared to alternative builds.

 

Also, keep in mind that to use Xerxes, you give up quite a bit of either damage or survival for your immortals. And as mentioned earlier, War Wagons are even slower then your immortals!

If you have issues with your Immortal's taking down buildings, I would strongly suggest using Battering Rams instead - They deal far more damage compared to your suggestion, can tank a huge amount of tower fire, and while still slow, are faster then War Wagons.

 

I still don't see why waste 5pop for 1 wagon. 5 Battering Rams is much much effective than 3 Wagons. 5 Immortals easily replace the Wagon in battle. If Palintonons are available, its not a question what will I build.
In my opinion, Xerxes should be change to "War Wagons move 15-20% faster, deal 20% bonus damage against buildings."
With this change, Wagons will be more effective against buildings but still weaker than Ballistas, Onagers and Catapults.

 

Ballista, Onagers, and Catapults are all used with a tanky frontline whose sole purpose is to soak damage so that those 3 can dish out damage.

Buildings only have .8 pierce armor, NOT .9 pierce armor.

But let's directly compare, yes?

If you decide to use Xerxes, you aren't going to use Immortals - You are going to use Sparabara's, which have low damage but are extremely tough.

With a maximum War Wagon build, they deal 312 ranged damage/second - This is 3x the damage output of the next highest small siege build, the Ballista, even taking into account the pop difference.

Now, against buildings, it's true - War Wagons deal significantly less damage vs buildings, sitting at 62.4 damage per second, whereas Ballista's deal 352 damage per second vs buildings, and absolute smash through walls due to their high splash damage (Which reminds me - When using any siege, if you need to break a wall, attack the shorter pieces - Splash damage effectively triples your damage to a wall if you attack those short stubby pieces)

But again - Turning War Wagons to Crush DPS is NOT the way to go - and 3x bonus damage to buildings is quite likely too much considering that War Wagons completely decimate armies at a much faster rate then the other siege.

I would suggest, instead, the following buff to Xerxes.

1 - In addition to seeing 20% farther, Xerxes increases the attack range of War Wagons by 20%. It's that way on pretty much every other Advisor that buffs line of sight - It also buffs Range by a corresponding amount.
2 - Xerxes also boosts War Wagon's damage output to buildings by, lets say 65% maximum.
3 - Alternatively, War Wagons ignore 30% armor.