Something to note: stats on the army screen are for the summoned group, not per man. Example: Human Militia Lv3 say they have 200 health. But they're summoned as a group of 4, so each man has 50 health.
Well, Grenadiers are one of the only units to do area-effect damage. I'm guessing here, but it's possible that the units are being hit multiple times by the blast as they move through the affected spaces. So that 70 damage blast is hitting them at least twice, for 140. If so, that gets worse for large units like cavalry.
Trivia: Most sides have Rifles, but Rifles tend to be poor. Their armour does not make up for their terrible health. If you're copying War3, do it right. The reason rifles were/are so beloved is high HP in combination with their armour; they're tanky and can take some hits. This makes their lesser range even more of an issue.
Supreis:*@Bloodly1, I don't know about the others, but I find that santa can't hold a candle to the orc heroes. Santa severely lacks offensive power.*
By the game stats, he is a slightly weaker Ogre. Santa has 100 less HP and 5 less movement speed. But of course, these aren't the true battle stats for either of the two, since they auto-buff with War Cry, which will also likely hit allies and increase killing power further that way. For someone you get free of all charge(8 shields is a heck of a cost, you must admit), I think he's fine.
A few minor notes.
Undead: Zombies have an unlisted trait; any corpses near Zombies arise as more Zombies.
Orcs: Shaman heal for half their listed Attack Strength. They will strike at full damage vs buildings ONLY.
Why do Spearmen always suck? They attack stupidly slow. This is also why Elves are so deadly-they're attacking seemingly twice as fast as anyone else on the field.
Beware the spam: AI doesn't follow your rules. It spawns units, it doesn't build them. THIS GOES FOR MERC BUILDINGS TOO. Be very careful when it comes to them.
No reason not to level everything to max so you can experiment with different unit loadouts.
It's fair to say that Santa Claus is the best hero you have. It's hard to justify 8 shields for a Hero who won't be deployed till late thanks to sheer cost.
Cavalry is generally the best option most of the time. Speed, power and defence.
I thought of something else. Half the reason you want/need so many people is because one dude carries one thing, multiplied by class. What if you could have carts or donkeys or something to help them carry? Sure, you might end up with the same amount of sprites, but...it's a thought.