Multipools didn't mess up doge, doge being a joke coin turned internet fad messed up doge coin. People were buying at prices that would have required over a million USD to continually flow into the coin each and every day to maintain given its billion coin per day inflation. If a coin requires all its miners to just hold it and not sell much in order to maintain its value then it's overvalued.

As far as casinocoin goes I'd be wary of changing things too much to try to thwart multipools since often times those battles turn into scorched earth situations in which nobody wins. Many of the countermeasure and coin parameters that have been tried have ended up having significant unintended consequences.

One mild and passive defense casinocoin already has is that it's a 30 second coin. Doubling hash rate will not halve block time since stale rates and orphans increase non-linearly as actual time per block decreases. At 30 seconds per block your real world mining output is probably going to be in the vicinity of 85% of the theoretical output. You're only getting 60-something percent once hash rate goes up enough to put the coin around 15 seconds. The more established multipool operators are aware of this but the average profit jumping small miner looking at a site like coinwarz often isn't. They'll pile in to whatever's on top of the list without a second thought. The one upside of that is that now you have more people with casinocoin and a small portion of them may choose to hold rather than immediately sell.

The one solution to volatility that I see is to just build the value of and demand for this coin. If that happens then steady hash will increase and the difficulty fluctuation caused by profit switching will lessen.