How to Dragoon per Second: A DPS Paradigm

[SunnyHirose]

1) Despite the dropped head and bracers I'm still aiming for Dervy's balanced set, and the reason why is because my team mates told me that Dervy calculated that starting from 780 crit deminishing returns start to kick in for this stat. Is this indeed true and if yes, is it so for every job?

Nothing special happens at 780 crit.

2) What should I do with cds outside of opener? I noticed I tend to delay cds if I see that my B4B will be up in 20-30 seconds so that I can allight for example B4B+IR+PS. Is it a bad thing to do? Shall I just use everything as it comes off cooldown and don't go for the "stacking with B4B" thing? I understand some mechanics call to the stacking, but I'm mostly asking in general, without regard to any specific encounter.

This is a bad thing to do, for the most part. It can pay off, but you will more likely delay long enough to cause a potency-per-second loss.