So I have the same card. I started messing around to see what would give me the best return. Started with Nicehash, cause well I am new to mining. But didn't like the return of $6 a day. So I turned to LBRY - which seemed to mine great, about $7-8 a day avg. Then I found Skein, I've been mining that since yesterday at 4pm - nice hash rate of 480M/hs. I think this will be the way to go. Going to let it run for a few days to see how many coins I can mine. I have bought a second GPU too, just waiting for my SLI bridge.
If you have a GTX 1080 Ti I hope that was a typo for your hashrate. A GTX 1080 ti should be getting 900+ Mh/s on skein - some versions of ccminer reportedly even top 1000 MH/s on skein. Which miner are you using?
I started with CCMiner2.0 but noticed I wasn't getting the hash rate that I should, so I found ccminer 8.08 by KlausT. My hash rate on skein is now 1040 Mh/s. Only thing I have noticed is with the pool I'm mining with, I have a high invalid hash rate, 5-10%. May be more to do with the pool than anything else.