I think given the fact u are a linker 3 u should have some High Stat to share with ur party, like HIGH CON or so. Going high INT is okay but any DPS wizard will have as much INT as you have and sharing it with archers/swordies wont do much, as oposite as having HIGH CON and giving huge hp boost to your DPS’s. It’s the “optimal” way to build a linker c3 given ur lifeline skill.
About the rank 7 choice, it is a very popular build the wiz 3 - linker 3 - Warlock in ktos, as an attacker support (have CC, utility with spiritual chain and lifeline and efficiency with JP) and also some great damage with quickcast + darktheurge in linked mobs for example. FF seems to be a DPS class but also a “self sustain” class, and i dont know the lifedrain interactions with your party (i think it doesnt share health recovered). But being a support/attack class with a self sustain is not a bad idea, as the healers dont need to babysit u so much sort of saying.
But if u want some more dynamic play i would pick FF cause it has lower cds and more skills to be used constantly (nghahundi, blood bath, blood sucking, bone pointing) as Warlock at the moment is almost 100% pole of agony and dark theurge only. Both choices are good ones, maybe Dark theurge has the best synergy with linker but we gotta wait to see what’s coming from C2 of both classes.
Sorry for the long answer, good luck.