At level 60 i went with a really simple build. Very effective as well.
15x crit damage, 15x crit rate, 4x +1% gun attack. WIth mediocre equips i still hit 3.0 crit damage, and about 1200 crit rate. I can still get 600-700 eva pretty easy while maintaining damage which is good for soloing and for DPSing trials.