Chaos magic. Is it necessary?

because the army isn't particularly strong, and they get crushed.

Crushed? It will be tougher against demons and Tier 3 units, and the Dark Elves aren't that strong either; they just overwhelm with numbers. But Dwarves and Humans, those are tough, and the Orcs with their rage are also strong, but without it, they're just weak. The Elves have good defense, and if you also level up defense on experience, they become very resilient, and you should also use "mass concrete." It's hard to quickly defeat Wind Dancers, and don't even get me started on Dryads and unique units.