...the hash is still close to historic highs and the coin continues to garner its security predominately from POW.
That argument is moot because Dash only applies it to 40% of its blocks (in economic terms).
Securing the protocol from hacking isn't the primary role of mining. In fact in economic terms it's not its role at all.
It has a far more important function in providing
monetary security by way of mediating competition for the new supply and thereby setting an opening price on new blocks emerging from the chain. The problem with Dash is that whatever hashrate it has is only applied to a minority of the chain. The coins that emerge from the rest of the blocks are received by their first holders at zero cost. (That wasn't the case when Evan Duffield first established the reward ratios).
It's exactly the same thing in economic terms as mining at zero difficulty. Consider your masternode as a zero-difficulty miner. (Cos that's what it is).
You can get away with this in some proof of stake chains where the adoption model is based on massive monetary/utility adoption from either use as "Dapp" fuel or for issuing securities the size of a whole nation's GDP or for creating currencies on top of currencies (such as Tezos new
USDtz for payments).
In the absence of such a commercial model, you need mining to store value. Bitcoin has an extremely high cost of extracting a block from the chain which means that for most people, in the absence of a multi-million pound Icelandic subterranean server plant, the only way to obtain it is in the secondary market (from someone who already mined it). This goes for EVERY BLOCK. There are no blocks in bitcoin that are given away for free or made subject to "zero-difficulty mining" as with Dash.
So who cares about protocol security from hacking ? It's in interesting technically but worthless in monetary terms because as Dash and other POS coins have demonstrated, it doesn't necessarily require hashpower to achieve.
Monetary security however is what people invest in and that DOES require hashpower if you're a bitcoin clone.
Look - somebody bought 3 masternodes in one gulp Dash/BTC yesterday. A market that normally trundles along in chunks of 20 to 40 DRK. Did that buy move the price up ? No, it went DOWN. Because masternodes have humungous bags of coins that they receive for free that they can just chuck onto markets all day long at any price with impunity. They even retain all of their 1000 Dash so what is there for them to lose ? (In fact their absurdly high level of revenue over cost exposes them to statutory tax pressure such that they lose out by NOT selling).
Following Spork 21, masternodes will be receive HALF of the entire supply of Dash at no cost. As long as that bleeding of blockchain capital continues, this coin is only going in one direction in terms of capitalisation. What investor that does an ounce of due diligence is going to invest in that kind of parasitical economic model ?
Finally, the broader market does not appear to share the view that hashrate is a "waste". Where are the "publicly listed masternodes" if they're so much more efficient in a monetary investment sense ?