1. I'm a little wary about making backstabs very weak early on, and then very strong later on. Rogues don't do much damage with regular attacks, they rely on criticals to remain competitive with fighters. This is especially the case in D:OS 2, which has removed speed and increasing AP. Rogues get the same amount of AP as fighters, and they only get a little extra movement from Scoundrel.
It's also inherently difficult to balance being very weak early with being very strong early. Early characters might be so weak that no one enjoys playing them to reach the end game, but the end game they might be powerful to the point of being broken.
The downside to making immune to backstabs/criticals enemies, such as all undead, means that Rogues won't be competitive at all in those fights and cannot really do anything. This could be a significant problem for several stretches of the game, since areas tend to have several encounters with the same types of enemies. After you escape Fort Joy, seven out of 11 combat encounters (64%) are versus an all-undead or mostly-undead group. That's a long time for a Rogue to be near-worthless in combat.
2. Blackjacks add crushing-type damage as an alternative to only being able to use backstab with piercing-type damage, which skeletons are highly resistant to.
3. You can make that argument and that's fine, although I think Larian disagrees. They have added some skills in D:OS 2 which give bonuses for being in Sneak in combat. Hence, they seem to think using Sneak in combat is a valid tactic.
And I have a second rebuttal: Guerrilla is a Badly Designed Talent because it is very situational. Most of the time you're better off using your AP for something else or saving it for the next turn. Even in the cases I outlined...
- Attacking from out of combat puts you into an unfavorable position in the turn order.
- You're using Sneak because of the power of the skill, and the skill is so powerful on its own that you can get benefits from it without needing Guerrilla.
- It can be very situational to have an enemy within 0 AP which will die from a dual-wielding backstab at 150% power AND the Rogue has 3 AP and does not have Adrenaline AND which no other party member could deal with instead.
I really doubt that you are going to be able to instantly kill something before a fight starts unless you're overleveled or are using a Source Point with Mortal Blow. Perhaps maybe a low HP enemy in the back. In that case, it's likely that the enemy was designed to have low HP, and even if your Rogue gets them, you are now starting out at a disadvantage because you're low in the turn order and in the enemy backlines, where there will be many more angry enemies.
