The dumper appears to be one guy by behaviour on YoBit. He dumps between 5k and 30k at one time. He's actually keeping down the price of Xios on his own as he's often the only person selling for hours at a time. He's actually pretty dumb and obviously not a trader as he could make much more BTC if he was smart by playing it differently, and still dump if that's what he wants to do.
Eventually he will run out of coins, even the biggest Xios accounts are not that large.
I think most people with masternodes are much more sensible, this guy is obviously one of the early PoW miners. Masternode guys are thinking long-term.
On the upside he helps the trade volume, though obviously the trade volume would be double if he was dumping at 12000-16000 sats rather than 6000-8000 sats, and he'd be making double BTC, but like I said he's not that smart and has no patience, probably a kid with ADD.