BRD/MCH does still look pretty close in damage.

If you look at Aiurily Ari in the logs, they are a competent player for both Bard and Machinist and it looks like the run content as both classes. I'm not sure how equal the two classes are geared especially with the difference in stat usage between the jobs, but overall their damage is very close between BRD/MCH but as well as that their party DPS is very similar regardless of what job they are playing, it just seems to shift the numbers around slightly.