Running 6 cards on a onda riserless mobo, 1500w at the wall, 490mh/s.
1575 clock, 860mv, 950 mem phoenix miner.
Something seems to be sucking up power unnecessarily in your setup - I ran same settings but w/ my mem just a touch lower (935), and only saw 215w/card - looks like you're at 240-245 for some reason, which is generally more in-line w/ the 90Mh/s config.
My rig has 4x 4000rpm fans (or 7x 3500rpm fans), just the mobo + fans with no gpu attached is ~140w.
Even so, it's less efficient that yours. Might be my psus hitting 90%+ load, I use the Evga 1600t2.
My Radeon VIIs run hot! I have the mem at 1500 core 975 undervolt 875 and they still get up to 80 degrees in my shed with fans blowing on them. Not sure I made a wise buy my hash rate for eth is down to 75. 80 - 90 make it a deal but I don't think it can run long at 85 degrees.
That's just the hotspot temp? If so that's within spec. Mine are 70-75 degrees in MSI AB, but 85-90 hotspot temp.
At 1500 core you can also go way lower with voltage, or bump up the core. Many of us run 850mv, and between 1500-1575 core for 80-82mh/s