Harmony - Troop Symmetry

7 days is a long time. Besides, 1-2 units of level 6, and even more so level 7, can mean much more than several reinforcements of lower-level units (especially considering more than one battle). For example, 2 Paladins can win a battle in which units of levels 1-3 would lose.
And the opponent still needs to get there. If the map is bare, then of course. But if not? Building up a town is something that happens in the first month, not in the middle of the game.
Although, maybe on lower difficulties the hero is... I haven't played on them. Aren't the neutrals weaker there?

personally, I've heard that "Heroes" is positioned as a "tactics" game, not a brawl. And tactics are not only the final battle (neutrals are not essential), but also actions on the map.