Is anyone else worried that the new power attack may be too good, epeciallly at low level?
New system: Full attack without power attack, using greatsword (for comparison purposes, we will use old rules for the greatsword).
At first level, fighter with str 18, expert proficiency, so about +6 (+4 str, +1 level, +1 prof) to hit vs AC 12, so needing a 6 to hit with the first attack.
Without power attack: hits on 6 (75% chance, crits 25%) doing 2d6+6, hits on 11 (50% chance, can't crit, crit fail 5%), doing 2d6+6, hits on a 16 (25% chance, can't crit, crit fail 30% chance) doing 2d6+6. Expected average damage 13(*.5) +26(*.25) +13(*.5)+13(*.25)= 22.75, round to 23. 32% chance of having at least 1 crit fail. (Doesn't reduce damage but may trigger a bad reaction.)
With power attack: hits on 6 (75% chance, crits 25%) doing 4d6+6, hits on 11 (50% chance, can't crit, crit fail 5%), doing 2d6+6. Expected average damage 20(*.5) + 40(*.25) + 20 (*.5) = 30 extra damage, with 5% chance of a crit miss.
So on average, power attacking is worth about +7 damage when full attacking at first level, assuming base damage per attack is similar to what it is to PF1.
Now this does assume that the fighter isn't using their third action for something else, as that third action attack isn't very valuable and may even be harmful. So the question then becomes what third action is worth giving up the extra damage from using power attack.
Note that these are averages, the actual results are going to be a LOT swingier. This is also assuming a critical hit simply doubles damage, which might easily not be the case.