So let me ask you, which is better, getting double damage 2/3rds of the time, getting +10 to attacks, or having one extra attack?
Depends on the situation. If you're up against a very tough opponent who can do tremendous damage with a single shot and you're low on healing goodies, I'd go with flurries. Same with many opponents, towards the start of a battle: I don't want to risk one of my team being stunned for a while and knocked out of the combat by somebody getting in a critical when mine failed. But I've used critical strike in combination with the saber crystals that deliver a heavy stun, and they worked very well, indeed.
To the Righteous belong the fruits of violent victory. The rest of us will have to settle for warm friends, warm lovers, and a wink from a quietly supportive universe.