I can't tell you why Suprnova performs badly like this (I had a similar experience) but I can tell you that i have not yet found a good reliable Mona pool anywhere. One of the biggest I found was asicminer.info and it consistently under quoted my hash-rate by 20-30%.
Isn't it possible that it's because of the latency? Are any of the pools near you? Some pools have definitely been having trouble with the newfound interest though. I find it hard to believe that /all pool operators/ are trying to exploit users, especially given I was a pool operator back in the day who ran my pool at a loss (1% bonus) to get more people to mine Monacoin.