You should be able to get a bit more out of them. I don't have that exact card, but my Gigabyte R9 290 does 880+. It was higher, but I turned the intensity down a bit to curb rejects.
You have 290's so you can probably set it to auto fan. They have their own fan speed controller and can do a good job adjusting it itself. You also have some pretty high rejects. You should be able to get them lower with some tuning. I'm at 0.3% now, but it can also depend on your pool, so check to see what's normal there.
Take some time and adjust one thing at a time and see the result. Try MSI Afterburner to tweak card settings in real time and watch the khs go up or down. Try going up in small increments. Also try going down. I know it sounds unintuitive, but under clocking works sometimes. You should be able to get the perfect setup in a couple hours.
For thread concurrency, try (n * shaders) +- 1. In my case, (12 * 2560) -1 = 30719. Don't ask why the -1. I have no idea, but it gives better khs. Give it a try.
Here's my config if it helps.
"failover-only": true,
"xintensity": "500",
"vectors": "1",
"worksize": "256",
"lookup-gap": "2",
"thread-concurrency": "30719",
"gpu-engine": "1002",
"gpu-memclock": "1500",
"gpu-powertune": "20",
"gpu-threads": "1",
"auto-fan": true,
"temp-cutoff": "90",
"temp-overheat": "85",
"temp-target": "80",
"queue": "0",
"scan-time": "1",
"expiry": "120",
"api-port": "4028",
"log": "5",
"temp-hysteresis": "3",
"kernel-path": "/usr/local/bin"
i can't change memclock to 1500 max in my card's it 1300 when i try more my rig freeze