Flurry and All in are useful early game when you lack any skills. They're also useful to finish off opponents when your other skills won't cut it, or to set up your next person to do so for the same reason. They do fall off, but I've used them throughout the game still, just significantly less than I did in the beginning.
I agree that those 2 skills can be useful at the beginning of the game but they fall off "really" soon. I stopped using them since level 6 I think.
For those that did not already saw the skill rating survey, you can have a look
HERE under section "SPECIAL".
Flurry and All in are in fact rated below average but I think it is fair. They are used as no CD finishers.
The problem is if you compare their usefulness to other skills like "Shield up" for example.
This skill should be as situational as the previous two and not an all purpose skill.
