I can assure you that users complain when the GUIs of DAWs start to run below 30fps, and really the expectation these days is that "performant" GUIs run at 60fps.
I am suggesting confirming if it is actually "slow" for the "key aspects".
You and the OP are just assuming it can't do whatever it is at "30fps"... if you're right, it will only take ten minutes if it's so bad, or an hour or two if it's subtle, to actually confirm whatever the worst thing is.
The "extra frame" I was thinking of is graphics pipeline latency, not redraw time.
Well now you're assuming what I'm assuming, which is fair enough because I assumed by your comment that you were saying the UI responsiveness isn't really a concern in DAWs. It's definitely a secondary concern, but people are accustomed to buttery smooth UIs and complain when they're not.
That said, I'd argue that even latency is still a concern for things like meters. If they are noticeably out of sync with what you hear then users will again complain.
