The volume is low because Bittrex doesn't allow US traders on their platform, which is Blocknets main exchange. Their DEX gets up to $10k volume on it's own some days, some days more, some days less.
Blocknet is MUCH more than just a DEX, which I believe most people are unaware off.
The best DEX is ViteX built on Vite (this is DAG project, like IOTA but with smartcontract). And they share 90% of revenue from trading fees to token holders (10% for owners). And this DEX is for multi blockhains.
Have you heard about uniswap, it's a dex exchange, currently lots of coins in there are doing x5 - 100, to me its consider the best Dex for now because it's really easy to navigate through, lots of people have been made awesomely rich from that exchange
Uniswap is limiting itself by being an ETH-based DEX. Meaning you CAN'T trade anything else than ERC tokens on it. This leaves out a LOT of projects, including BTC.