All mentions - purely arbitrary, purely theoretical calculations.
Solo mining:
Claymore takes 1%, you are left with 99% ETH PoW time (effort)
Ethermine pool takes 1% of your 99% ETH effort
Ideally, you should be left with 98%
Dual mining:
Claymore takes 2%, 98% left, can be truncated to 95% (dual gives more incorrect and stale shares)
Ethermine takes 1% of your 95%
You are left with ~94%
Siamining takes 3% of your Sia effort, Claymore takes none
PS:
1. Siacoin is not anymore viable for GPU mining (difficulty and net hashrate skyrocketed).
2. Luck factor makes the effective hashrate fluctuate 10-15% up and down.
3. For AMD RX, optimal dcri values can boost the ETH hashrate by 2-3%. However, incorrect share ratio tends to be about 1-2%, so it levels out.
-dcri 85
This is your problem. Too high dual mining intensity crashes the GPUs.
While that's true, he must not be keeping up: dual mining is dead for now - until Claymore gets his 10.7 version out (probably a week from his previous statement here?), it will have at least one new algo supported that isn't already being sucked dead by the ASIC miners.
"Give it up!" for now...