Heroes 5.5 WarGame Edition - Tactical Edition.

Regarding the more complex mathematics:

The "200% or x2" model for boosting your own unit and "50% or /2" for debuffing the enemy works when there are only 2 units involved, your unit and the enemy's, and no other active participants (including heroes).

As soon as other participants are added (units and heroes), the model starts to work differently, based on the sum. For example:
- Increasing the initiative of 1 unit by 2 times = increasing its strength by 1.5 times (+50% to the unit)
- Decreasing the initiative of 1 unit by 2 times = decreasing its strength by 1.5 times (-33% to the unit)
If, for example, we have approximately 4 equal units on each side, we get a change in the balance of power in the first case from 4:4 to 4.5:4 (112.5%), and in the second case to 4:3.67 (109%). Obviously, in the first case, the relative strength of the army increases more.

Furthermore, duration also matters. A simple example: if we increase the initiative of a unit with 10 initiative by 2 times, it will perform 2 actions in 1 round (+1 extra action). And if we decrease the initiative of a unit with 10 initiative by 2 times, it will lose its full action only after 2 rounds (performing 1 action instead of 2).

In short, "similar" buffs work more powerfully and have a faster impact, while "similar" debuffs work less effectively and have a slower impact. This is the fundamental difference, which is very noticeable in practice with large numbers (on the order of doubling the initiative).