Doubts about the correctness of pumping \ "Blade of Shadows \" (Divinity: Original Sin 2)

Hello everyone. Completed the game at the "Easy" and "Classic" levels. Both times four of us and always was in the "Blade of Shadows" party. And both times I was tormented by vague doubts about the correctness of its pumping. In the advice of seasoned players, it is recommended to invest in "Dexterity" and "Perception" for damage and crit chance. And also in "Two weapons" in order to avoid the penalty and reduce the amount of AP per hit with one blade.
I understand that a thief always has a 100% chance to inflict critical damage if he hits in the back, and in two passes I could not do it just a couple of times because the enemy was standing against the wall. However, there is a teleport that will always move the enemy. So does it make sense to invest "Horn" in "Perception" and "Two Weapons"? After the end of the game, I decided to test it, since I am going to play on Tactics. He took the Blade in the state in which he finished the game:
Dexterity-54
Perception-37
Military-9
Two weapons-9 The
art of assassination-7
Talent "Partizan" taken.
He took one opponent and tested with a blow "Rupture of sinews". So, with the above characteristics, the critical damage was 845 units. Neither Chameleon, nor inviz through "C", nor both of them together did not affect the damage. Checked and sitting in a barrel in place and walking around the field, no result. I conclude that the "Partisan" skill does not work.
Then he removed 9 points from perception and invested them in Dexterity:
Dexterity-62
Perception-28
Military-9
Two weapons-9 The
art of murder-7
Talent Partizan taken.
The damage became 982 units, that is, increased. I could not remove all the glasses from perception. they are on gear, but the result is clear.
Then I decided to take off my glasses from "Two Weapons". He took off 6, the rest on gear.


Military-9
Two weapons-3 The
art of assassination-7 The
talent of the Partisan is taken.
The damage became 921 units, that is, decreased. We can say that the points invested in "Two weapons" affect the damage. However, we have removed these 6 points, but have not invested anywhere. We invest 2 of them in "Military affairs" and the damage becomes 970 units. And we still have 4 points left, but I did not invest them in "VD". because of the gear reached the maximum and the points were not invested. However, if 9 points are invested in "VD", then this will be more damage than in "Two weapons".
For me, the conclusion is obvious: We invest in full in "Dexterity", at least in "Constitution" and the required amount in "Memory". We change "Partizan" to "Mnemonic". No "Two Weapons".

And yet, no matter how many points are invested or not invested in "Two weapons", the number of APs per strike remains 2 APs. Yes, there are, of course, strikes that require 3 MP, but they require 3 MP for any Two Weapon condition. I understand that "Perception" affects "Initiative", but I never had the first move in both playthroughs. the melee had the maximum initiative. And he was also responsible for discovering hidden places.
I also tested the "Finishing Blow". If you hit them from invisibility, the damage is doubled. It works, and invisibility is both a Chameleon, and a potion of invisibility and Stealth through "C". That is, in this blow fictitiously "Partizan" works. It is not clear who would think of giving three MPs for "S"