This is exactly why my default opinion, particularly about non-Celtics, is usually heavily slanted towards a consensus of multiple advanced stats.
Why would my guess about Brogdon’s D be significantly better (or better at all), than looking at a combination of DARKO, RAPTOR, etc?
We cen certainly come up with team specific reasons that those stats might under or over rate certain players. But do we know how legit those reasons really are? Or how much weight to give it? I’m kinda doubt it.
FWIW, I agree that we should be careful in the weight that we apply to defensive advanced stats because they're still young and developing. And folks have attempted a "blended scotch" approach, including some pretty smart professional statisticians. It's always good to try to ferret out the outliers one way or another.
All approaches for isolating the outliers have some risk. Blending them, while a useful tool for playing around with the numbers, seems to simply factor in the outliers and water down the (potentially) better numbers. A second approach is to drop the outlier altogether (the "Russian Judge approach") and simply take the means of the others, normalized. The problem with that approach is that sometimes the outlier is just a better number. We've seen that in baseball stats over the years--even one version of WAR itself was recently recalibrated (the BRef version IIRC)--and that shit has been out there forever.
I think that factoring in multiple sources (like you wrote) is still a requirement and that blending them is just watering them down. But we still need to apply a lot of eye test and hedge things in general. You see a lot of "Well, LEBRON and RAPTOR love his defense, but DARKO isn't so sure, and this other one..." It's not definitive by any means, but if three or four sources agree with your eye test, and if you're also factoring in their age, measurables, their current situation, etc., it gets you a lot of the way there. My .02.
