Balanced Units - A minimal balance mod for units

The enemy will position themselves in a way that makes attacking multiple units inefficient or impossible. I would estimate this as a +40%, or at most, +50% damage increase.

It's easy to say, but harder to do, and for such arrangements, you have to sacrifice something. Whether it's 50% or 60% isn't that important; the goal isn't to perfectly balance the upgrades, but to make them comparable.

I don't know. Casting invisibility also means automatically losing one turn. I think three turns was fine. Assassins just need to be made stronger. Remove the penalty to ranged attacks, for example. Or give them armor-piercing, like crossbowmen, for close-range attacks.

The issue isn't in the endgame, where assassins are already good because of their ranged poison that ignores the defenses of higher-tier units. The problem is breaking through against hunters; it's too easy to bypass them with invisibility and chaos, and they are already being dealt 1.5 times more damage when the duration is reduced. There's no point in buffing assassins when hunters are clearly overpowered on their own.

100% chance to hit without dexterity. But you could give them retaliate; this would allow them to maneuver fearlessly in any way that is most advantageous, without destroying the original concept of a "glass cannon" for this tier of ranged units.

Without dexterity, they probably won't take the alternate upgrade. Retaliate is weaker, and I'm not sure it will be competitive.
Currently, we essentially have: alternate lizard units with 12 initiative against 11, chance to hit against accuracy.

Although, now that I've recalculated, it's possible that 100% chance to hit will be enough to make it competitive with accuracy, without retaliate or dexterity. It makes sense to try it out so as not to create new abilities or stats.