Some issues I see with DRK. tl;dr at bottom
Here is a miner that does 40% better than stock:https://bitcointalk.org/index.php?topic=616786.0Yeah he is in violation of the GPL but he has 30 days to comply in which time he will rack up quite the stash since he is skimming 2% of the hash. And this is the public version. Private versions go much further.
My observation on 2x r9 280x on multipool.
hashrate in sgminer up 35%, el. consumption up from 265w to 300w. Payouts around 5-10% higher (not enough testing, to be sure if it's any gain), temps 5 degrees higher.
summary:
sgminer shows big increase of hashrate, power consumption higher 10-15%, payouts not even close to 30% higher, probably around of higher power consumption mark, max to 10%.
And my data is with disabled 2% fees (using: P C 0 ).