General

Angel ray is not only your main attacking skill for 4th job but your strongest as well , get decent % int and max our AR and Arcane aim and you'll be a pro bishop.

Yes. You need it unless you're making a buff mule. You can try to find it by bossing, but I heard Zak's drop rate for books has gone down.

If youre gonna be attacking, yea, buy it. But if you rope hang, its not worth it. Just zak/hilla everyday till you find it

You definitely need it
Unless you want to hang on a rope buffing all the time o.o

if you want to attack, then yea, it's a good skill to have. or you can stick to using shining ray. AR is a lot stronger though.