I don't think MCH has as much to gain with cheese as BRD though; attacking two legs on A4S, for instance, is a lot less valuable. The ceiling seems lower despite the same amount of effort. Also River of Blood / Straighter Shot is a higher-variance system than MCH's procs, so BRD can benefit more from outlier levels of luck. It's true that there's no ideal place to look for a representative sample of "honest" top play, but I'd think the 95th or 99th percentiles would be closer to it than the 100th would be.

A3S doesn't have the "you get to add damage that doesn't matter" element, but it is extremely Bard-friendly. It just doesn't feel as much so due to being juxtaposed to A1S and A2S. Phase 3 consists of waves of adds spawning on a circle with a 5-6 yalm radius, phase 2 has two targets and a DPS check where BRD can leverage Flaming Arrow and Rain of Death but MCH (I assume) doesn't want to go to Bishop... it's actually humorous how conveniently constructed it is. A difference as simple as the Lubricants starting on the outside and working their way in, and BRD vs. MCH on that fight would be a much different story. I'd be surprised if there's more than maybe one fight in Midas that is as skewed towards Bard as A3S is.

Really, the best measure of self-contained DPS is possibly going to end up being Stone-Sky-Sea, but it's hard to account for that variance. I wouldn't bet on the top times going to MCH for-sure, because godlike River runs certainly happen. But I would be surprised if the top BRDs' typical times (with more average numbers of BL procs, basically) are better than your times when you get a more average number of GCD procs.