If you want to use math you should be attempting to determine the amount of extra damage per round that your increased chance to crit gives
I suspect it's very little
Let me see. This is for the character at level 12(fighter 7/rogue 5) assuming I keep the same gear loadout I have right now(I will likely have much better stuff by then). Also setup sneak attack to "ask" to proc on reaction so I always use it on some critical hit.
Regular attack: 9 + 1d6 damage = maximum 15 damage)
Critical hit attack: 2x(9+1d6) + 10 flat necrotic damage = maximum 40 damage(28 + 2d6)
Critical hit sneak attack: 2x(9+1d6) + 2x(3d6) + 10 flat necrotic damage = maximum 76 damage(28 + 8d6)
Assume I quaff a haste potion and use action surge on the first round of combat. That is 5 attacks. Assume at least two of these attacks are critical hits.
That is 161 maximum damage output in one round(101 flat + 10d6). 68 of that number comes from critical damage.
That is not to mention other shenanigans I can use, such as the amulet of branding once per long rest(which itself doubles damage by making enemies vulnerable - meaning maximum 152 damage on a single critical hit).
I'm sure this is not the best damage output build in the game, but it sure has more damage and more function than the assassin gloom stalker build everyone uses. Specially first round(which is also where such alternative build would shine)