So what our Blm true numbers.

[Zencurse]

ilv96 with ilv95 allagan stuff and pot and food i pulled 310 in T8 and our BARD doesn't FOE. I don't even use poison pot.
So if add FOE. I would be able to pull 350 if my RNG is good. 400 isn't a mystery if you know what you are doing with your GEAR and ROTATION and...LUCK
Because I could pull 320+ at dummy if I'm lucky with my RNG that doesn't killing my dps.
Oh and my avg dps is around 290.

I'm ilvl 100 with the 110 staff, our bard foes at the beginning of the fight and momentarily at the end of the fight (So rather sparingly, we get approx. 30 seconds of it) and I do 340-370 (RNG dependent). So yes, if I had foes the whole time I could easily see 400. But again, the point is Black Mages have a lot of RNG and foes req dependency to pull those kinds of numbers and in attempting to answer the OPs question I'd say you'd have to consider what the black mage player means by "400 dps" to be a combination of luck, at least mild skill, the fight itself, and consider the bards role. Not their, testing on the dummy dps.