With a Focus Chip and her Skill left on forced manual, SIG556’s DPS is actually quite decent. That said, she stuns herself repeatedly and is overall quite awful to actually use.
As such, SIG556 is not recommended.
Full analysis
SIG556’s Skill does set her to her “max RoF” of 150, but can’t actually shoot faster than 116 RoF during her Skill due to MICA errors.