You probably noticed that there have little mention any helms for BL in Cabal. A helm is what makes or breaks the BL class(cabal alz), and you have 3 choices, each with their bonuses and disadvantages.

For the 16% craft helm with 5% rate in first slot, extended (the 7% rate / 40% crit dmg helm) which is the basic choice for most bladers, it provides almost maximum CD in helm, while at the same time improving critical rate. Your CR will be 42% unless a Warrior or Force Blader is in the party.

This type of helm is good if you plan on being a party member most of the time, to have 52% rate at least from the party debuffs (FB). You might find that 90 seconds of 42 rate is not enough if you want to solo stuff, , so you will most likely go in BM + Aura to compensate this. We provide Cabal powerleveling service for you.

Since you are forced to go aura to compensate the lack of rate, you might as well not use the helm at all, but use a 36% one, since you get 15 rate+ from aura. Then the 7/40 helm becomes useless, if you are forced to go BM+A, and it is therefore an expensive and unneeded investment (for the 4% extra CD that you gain).