well, I'm trying a more "fair" (from my POV) approach to squads .... and in my vision squad sizes are 1, 4, 10, 20, 40, and 80 soldiers in number.
Obviously there are advantages to having 80 soldiers, but its not an all-powerful choice either. Sometimes having Faster, Stronger, and more Heavily armored small squads is the better choice.
And ... Heroes .... even an unarmored, poorly armed high level/ high stat Hero should be able to do some damage while being killed by a regiment of 80 grunts with hammers. Meanwhile a well equipped high level/ high stat Hero should be able to really do some damage.
And as far as magic ... having more "protection spells" and "dispel magic" would be nice. For instance, with high-level magic maybe things like "protect army"-wizard A, "dispel protection ALL"-Wizard B, Wizard A- "Reflect Magic all", Wizard B-"Dispel Reflect" ... Wizard A casts "Reveal" and sees that Wizard B's army all has reflect magic already cast on them. Wizard B casts "Fireball" onto a squad of swordsmen. Wizard A casts "(Hidden)", Wizard B gets cocky and casts "Fireball" on a party of DeathKnights. Fireball gets caught in a "Magic Trap" (lets assume Fireball cost 10 mana to cast), and Wizard B gets drained for 20 mana!.
Wizard A then casts "Double Cast", Wizard B casts Fireball on the squad of swordsmen. Wizard A casts "Dispel Reflect ALL", Wizard A casts "FireStorm!"
Wizard B has run out of mana .... Wizard A casts "FireStorm!" ... Wizard A is out of mana ... Wizard A's Army continues to fight Wizard B's army, eventually emerging victorious.