In my opinion, FA, FB are the best classes currently (and will stay this way for at least another 6 months). I am not gonna get into FB but here is why for FA.

In war: FA OP range and aoe is ridiculous plus their quickmove + unroot make them very hard to kill. If you are good, you don't even get hit as FA. (you can ignore defense as FA and invest in damage). FA damage is quite high as well and very strong vs 1 target. The new war is FA's farming zone you can't farm better than FA in that war.

In dungeon: if you solo (so anything below afi) your damage is very good since boss fight is always single target and if you have good gear your bm2 is very powerfull. In party (afi and up) FA boost up everybody attack rate, 77 base that very good for tempus.

I just want to say what I think so don't be too aggressive )