Well man the highest total Hashrate I have achieved on average from the site, this being over 20 minutes I'd say is 415/420. Lol my 7950 is mining at 607 k/hash and has 101 accepted and 2 rejected shares, my 660ti is mining at 150 with 243 accepted and 4 rejected shares and my cpu is mining at 50 with 78 accepted and 2 rejected shares. So I don't see what is up.
you have to small thread concurrency. data overwrites itself, and yes, you do 600k hashes per s, but your miner cant find correct one [they are destroyed] and discards them, effectively finding only very lucky ones that are ready to submit before they get overwriten.
pool is simply guessing your hashrate by number of shares submited. pool works just fine.
make a new txt file change extention to .bat or .cmd and try these settings:
setx GPU_MAX_ALLOC_PERCENT 100
cd C:\yourpath\cgminer\
C:\yourpath\cgminer.exe --scrypt -o stratum+tcp://stratum.give-me-ltc.com:3333 -u youruser.yourworker -p yourpass --thread-concurrency 22400 -I 19 -g 1 -w 256