is DEX useless now?

Never spend NX to fix a character that is worthless at level 120. There just aint no point in building Cygnuses for anything other than to get it to 120 as fast as possible. With the BB update, 120 is easy regardless of class and stats.
If it was a Brawler or a Warrior I'd say yes, reset. Dex really is worthless, and if you aim to be among the high tier damage dealers 160 Dex aint that hard to get from equips, just expensive.

i actually picked TB because i liked them ._.