This seems like a drastic redesign of the champion system.

The latest patch helped with this balance problem somewhat by giving champions more HP as they advance.  And equipment advances with champions at the same rate as with soldiers, because the same tech applies to both.

Maybe provide some other army-specific talents that champions can have?

Also, the way attack and defense is calculated for groups could be tweaked.  Instead of a group of 3 soldiers with 5 attack each getting a 15 attack, they should perhaps get 3 attacks at strength 5.  The math is slightly different, and should further balance the champion vs. soldier group balance problem.

I know Brad mentioned they are completely revamping tactical combat so this idea is probably moot. One idea I thought of would be to implement some kind of fatigue debuff to attacking/defending units in combat. Logic goes that if a unit is actively engaged in combat, it is getting tired and stats suffer. I raise this point because in my current game I have an army of 11 fully geared champions marauding across the map killing massive groups of armies (armies in Umber cities of 6 groups of 9 Sions, full stacks of Pariden Lord Hammer and heavy plate, etc). My champions aren't cleaning house from massive fireballs and such; they are doing it my swinging magical metal blades and dodging/blocking damage. That has to get tiring. If a unit "rests" during a combat turn, their fatigue bar would replenish. Maybe moving around doesn't hurt or help. If units/champions got tired and stats suffered, a million peasants could then kill an elite champion or unit, no matter how rocked out the unit is. They could implement some spells and abilities to help offset fatigue as well. Anyway, that's my two gildars.

I agree that it is currently too easy to have dozens of champions running around.  In fact it's possible to win a game without training a single combat unit.  I think there needs to be some mechanism to limit the number of champions a player can support.  Some sort of upkeep (Gildar, materials, population, food or something combination) would help to limit the number of champions while still allowing for players to choose for themselves how many champions they want.  If they want armies of champions running around then fine but they'll have to pay for it in some way.  Either that or get the AI to make units that can actually hurt/kill high level champions.  The way things are now, champions are like regular units except they can be instantly trained and equipped.  

Since Master Of Magic Heroes are an isue. If you make them unique so that only one faction can get certein hero then we get random element into the game. 

Making them more expensive doesn't solve the problem how it is now. 

Making items harder to get will render them useless. 

Adding passive abilities like +10% to attack for every unit in stack will make "stacks of doom" present. So that doesn't solve anything.

I would add counter matter to the game. So that you can easily get a hero who could counter the threat quickly. Something like one hero gets ability to assassinate other can get protection from that etc. One hero is extreamly qiuck so other has lot of snares. Such change would give everyone a counter to a threat that well eqiuped powerfull heroes bring. Also this change could give more tactical feeling.

Having the possibility to qiuckly assembly a defensive army with a hero who would render even most deadly foe weaker could balance things out.