But DAST is more about proving SAST findings to remove any doubt. I prefer to use a 'directed' DAST approach to keep it fast and in-band to the pipeline.
By 'Directed' I mean, we have a map of endpoints and associated vulns from our SAST and I use that to focus the DAST on specific issues on each endpoint with as much other info as it may need (DB?).
I'm not a fan of IAST right now but then I haven't really used it.
DAST is the proof point on why data flow analysis is key when you consider that DAST is really about abusing user-controlled inputs. So an understanding of user-controlled data flows in your software is so important to identify OWASP Top 10 issues, most of which are injection-related in one way or another.