This came up in a different thread about trying to find the damage cap on focus spells, and Flury of claws was presented as top damage one for targeting 2 creatures, but looking at it, it lacks any language suggestion it does double damage on a critical hit. By RAW, spells have to say what they do on a critical hit, so currently Flury of Claws only does regular damage on any result of a success or better.
This absolutely could be an accident in need of errata. It also feels like it is possible the usual line about doing double damage on a crit got removed on an editing pass by someone looking at the math and dealing the damage output of the rank one focus spell was too high. A lot of players do not like doing the tactical shenanigans to maximize crit potential and I could see the appeal in having a focus spells that just does as much damage as possible once you get a success. Not doubling on a critical hit is a way to offer that. However, I think very many players will feel like the lack of other spells that do the same will mean this HAS to be an accident and will assume the spell should just be played assuming the doubling language is there.
I understand this impulse and house ruling things that feel like mistakes is a great way to play, but I don’t think it is good for people to use their assumed errata house rules when putting that spell forward as an example of what current game expectations are.
1d8+1dd4 per rank without doubling on a critical damage is significantly less than 2d6 per rank that does double on a critical.
Maybe this will get addressed in an errata or a FAQ, and for home play, I think people should do whatever they want, but I don’t thing PFS can make any assumptions about it, nor should probably 3rd party developers designing new abilities intended to balance with existing options.