Heroes 5.5 WarGame Edition - Tactical Edition.

This perk doesn't do anything interesting, it's very weak and doesn't scale.

I'll say this right away: I'm just skimming through, so I don't know the intricacies of modding and your capabilities on the Heroes engine, but here's what you can do with this perk:
What about synergy with luck? For example, if a unit's luck triggers, the chance of a critical hit at that moment also increases by:
Luck amount * Hero level / 4
Examples:
0 * 25 / 4 = +0%
1 * 25 / 4 = +6.25%
2 * 25 / 4 = +12.5%
3 * 25 / 4 = +18.75%
4 * 25 / 4 = +25%
5 * 25 / 4 = +31.25%
5 * 30 / 4 = +37.5%
5 * 40 / 4 = +50%

Also, with a full proc, you can add damage to the final value (i.e., the final damage number will be 300%, and we will improve this number by a percentage as well). Not much, but just to have something.

But in general, you can balance it yourself.