Honestly my champs are not too strong.  If you take off all your gear that you find, and don't use blizzard or fireball it's more balanced.  Of course one of the main problems is monster stacks dont' seem to, and Armies definatlly do not have any levels.  When a level 20 champ goes against an army, and the army is level 1?  Yea, they SHOULD be destroyed.

What would help the balance issue is make it so armies can be made above level 1 and monsters can level up as time goes on.  We could even add a slider to how fast monsters level on a map to present more challenge options.

Armies should have more ways we can make them build at higher level to present opponents with something other than fireball fodder.  mabye make it so base level of the unit is same as level of a City?  More buildings that add levels or level ones that are picked when you level up that add 2-3 levels each to help with city specialization?

Another option would be add a way so you can train the troops longer when you design the unit in the unit design.  add a % to its cost and the level of the troop get's higher and higher.  Can use tech to unlock how much you can do. 

Just some Idea's.

My answer would be, that champions and regular units, shouldn't be measured on the same scale at all (at least not in the end game), instead they should have different functions.

I would prefer if my champions where leaders of men and slayers of monsters.

So a leader type champion should be a great boon to an army, and a warrior type champion should be great for taking out even the toughest monsters, but a single hero shouldn't be able to take out entire well-equiped armies. 

A dragon on the other hand should be able to lay waste to armies, but be killable by a great hero.

Ideas that could help with a "hero beats dragon beats army beats hero" scenario, could be stuff like:

- The existing overpower mechanic.

- Heroes not being able to slaughter multiple members of a unit. With a standard attack: one hit = one kill (special attacks, should break this rule)

- Monster effects (debuffs/auras) that hinders units a lot but doesn't affect champions as much. For example, a dragon could have a battlefield "fear 3" effect, which would have all enemy units lose 3 attack in a battle. The hero would then be reduced from 30 to 27 attack, while the 5 spearmen each with 6 attack, would be reduced from 5*6 = 30 attack, to 5*3 = 15 attack. (numbers are made up for the example)

Mages are an other matter, their power, should be constrained by the available amount of mana. Spells should be powerful, but be expensive, so you would have to think hard about when to use mana.