Even 7.6 GH/s seems wrong. Where are all these people? Usually if a new coin has even 2 or 3 GH/s net hashrate the forum is moving a lot quicker and also the trading volume. I doubt there is 7.5 GH/s worth of solo mining going on and only < 100 MH/s of pool mining. With a diff this high people would be pool mining at this point but the pool hashrates are dying. It still seems bugged, it doesnt seem like very many people are mining this at all.
It's just people not mining on our pool. Since fusioncoin is merged minable, it's easier to have high hashrate, cause you don't know who is merged mining fusioncoin. The scenario could be quite different from other coins.
BTW, there's no trick in hash rate calculation, just grab average block time for scrypt blocks and difficulty, and we have hashrate=(diff*2^32/avg_time) or roughly 4.2GH/s * diff / avg_time
I could even show you a gist to calculate that, or you can check our source code for function "getnetworkhashps"