WB does make sense, for some reason I've found the Intels to handle WT worse than other drives on writes. I almost always end up using DCE using the Intels

Did you try raid-10 vs raid-5?
I haven't spent much time with raid-5 on the 9260, it might not be the best performer?

The pcmv scores seem to be on the low side.

2R0 X25-V on the 9260 scored > 53K. (not running OS though)

Speaking of BBUs, mine suddenly stopped working.
[Fatal] Battery needs to be replaced, SOH Bad.

I started a learn cycle but that didn't help, it completed the relearn cycle but as soon as it finished the messages popped up again.
It's been acting strange ever since I got it.

You'd better configure the Alerts just to be on the safe side.