So, I see a lot, and I mean a *lot* of hero stacking. People place more than one hero in their stack to gain an advantage. Now I've reaped the benefits of this by accident (two heroes in one tower), and I see how the chaos and morale can work together. But what is the overarching rationale for this tactic? Do heroes each gain full experience in that situation?
If heroes both gain full experience when participating in a battle together, then that needs to change. Maybe I'm a bit too traditional, but it looks like an exploit to me. There's a reason heroes have separate abilities, and if you can combine two for a fully-functional superhero with the advantage that experience for slain enemies goes twice as far... well, that says it all. I'd like to take this opportunity to preempt irrelevant arguments about heroes being able to gain abilities through items and unit pairing: that's within the intended scope of the heroes' individual limitations.
The rest of this is a technical suggestion to the creators regarding Archons, so do yourself a favor and skip it if you're not interested.
Also, Archons should maintain the ability to negate their full amount from each hero in the enemy army. If two heroes are providing two separate bonuses (+7 morale Paladin and +9 chaos Dread Knight for example) then a blue Archon should negate 6 morale from the paladin and 6 chaos from the dread knight. You can balance this by taking the highest attribute of each hero, applying the negate to each, then comparing the attributes of each to determine what is used in battle. So if your Dread Knight still has a +3 morale item, the game behaves as if he were the only hero, providing +3 morale and +3 Chaos (Note that if the dread knight were alone, he'd have +3+3, if this is not taken into account then you're punishing the player for including the Paladin by reducing the total bonus to +1 morale and +3 chaos). It might sound complicated, but it's a balanced solution to stacked heroes and archon negate problems; it's also simple and effective in practice even if the player doesn't understand the precise mechanics behind it. Whether you choose the highest remaining attributes of all heroes after the negate or use an elimination protocol to narrow the choices to [the two original highest attributes, now modified][or][the highest total of morale/chaos remaining to one hero] becomes a matter of whether you wish to reward hero stacking or simply avoid penalizing it. I'm wary of a world in which Archon abilities can be circumvented by using two heroes in stacks of 8; also wary of a world where Archon bonuses are applied imprecisely and players actually find themselves punished for having two heroes present in a city.