Must be my config then.
I've got a great hash rate around 880 each card with 820-840 WU but my rejects are huge.
using asia server atm
try to go for high thread-concurrency + low intensity
getting 1~% reject
280x @ 680kh/s:-
thread-concurrency : 28672 (2048 * 14)
gpu-thread : 1
intensity : 18
gpu-engine : 1100
gpu-memclock : 1500
7950 @ 590kh/s :-
thread-concurrency : 25984 (1792 * 14.5)
gpu-thread : 1
intensity : 18
gpu-engine : 1050
gpu-memclock : 1250