Larian Studios Forums Divinity: Original Sin 2 Divinity - Original Sin 2 - General D:OS1 was MUCH better before grenades

I haven't used Rage, so I'll take your word on that for now, but as for Guerrilla, I've done the math.

Single-wielding attacks cost 1 AP
Dual wielding attacks cost 2 AP.
Guerrilla adds +50% damage and the Sneak to make use of it costs 1 AP. That additional AP has to be factored into the cost, whether you use the attack on the same turn or the next one.

Using Guerrilla with 1 weapon does the damage of 1.5 attacks for the AP cost of 2 attacks.
Using Guerrilla when dual-wielding does the damage of 1.5 attacks for the AP cost of 1.5 attacks. (In other words, you're not any better off using it than you would be for using normal attacks).

It is only useful when attacks do not cost AP - as in you enter combat through a sneak attack.

You get 4 AP per turn, so entering Sneak the turn before instead of saving that AP for the next turn only is a net AP benefit if you have 3+ AP left at the end of your turn and would "lose" an AP when the 4 from the next turn is added to fill the 3 empty AP bubbles. If you have 1 or 2 AP at the end, Sneaking will prevent you from being seen, but it is one fewer AP than you would have had on the next turn.