Dicecoin.io redirects to duckdice.io for certain when I go there. It's because I'm going to it from a US IP and if I use a VPN I can actually get to dicecoin.io. Cryptogames.io also blocks USA users although that was a later in the history of the site when they started doing that.
USA is blocked by many dice sites but are you sure dicecoin redirects to duckdice if we visit from US IP? This sound quite serious now, if all three of this sites are connected than duckdice might also loss all the reputation they have earned so far. I have also played there and really like the user interface and support duckdice have. 
This site was legit until it wasn't. The same could happen to any site you play at. Primedice could decide to stop everything one day and keep it all. I'm not out any cash overall. I'm missing about $30 in LTC from the last two times I tried to deposit. The only reason I kept playing there is because I felt like I could win easier there than at another site. At this point I really want to know the scoop just because.
...also I found a person/contact julia@cryptogames.io and it looks like her name is Julia Brown and she lived in the UK. Not sure how true that actually is though.