can be combined with the power stance
My problem with power stance is that it sucks. It's literally worse than not using it, unless you have a 100% hit chance with it.
Then it's the exact same as not having it if you have a two-handed weapon, but still worse with a onehanded.5 is 125% of 4. With two handers it's the same AP>Damage.
4 is 133% of 3. With one handers it's more AP per damage.
Accuracy stance isn't the worst, but whenever I feel I need accuracy I personally like using blessed earth to buff the whole party.
This is entirely correct... if the measure of whether an action is smart or not is damage/AP spent over time. If e.g the game was about whaling away at million hitpoint strong target dummies, you'd definitely have a point.
But that is not the case. Most fights feature multiple enemies with hitpoint pools of various sizes, and cutting down on the number of enemies to limit how many enemies act against you each turn is important.
As an obvious example of what I mean, assuming you are going to hit in the first place, if you can kill something in one hit with power stance that won't die in a normal hit, then it is a question of one hit for 5AP or two hits for 4AP each (or one hit for 4AP and somebody else in your party spending AP on doing the rest of the damage). NOT using power stance in that situation is foolish - not only will it cost the party more AP in total to kill the enemy, the enemy may even get an extra turn to act against the party in.
The same goes when you are not at the last hit. Let's take the typical example of a fighter with 10 AP, who can either hit twice for 4 AP, with 2 AP left over for next turn, or make a 4 AP and a 5 AP hit, or two 5 AP hits. Which of these three options is the smartest depends entirely upon the remaining health of the target and the actions of other party members.
THE argument against power stance is not that it sucks, because it doesn't, but that it is a stance that needs quite a bit of fiddling with to benefit from, being toggled either on or off on an individual strike basis as the circumstances require in order to maximize its performance.
As a general rule, it should be used at maxed precision when doing so will with a high degree of certainty result in killing off enemies faster without the risk of misses, or when there is a risk of misses and enemies' armour is so high that the extra damage justifies both the increased cost and the increased risk.