dollar cost averaging does not in reality mitigate the volatility risk...

Consider the scenario where you are invested in 100% indexes and get hit by some black swan event resulting in >70% drawdown. Odds are that you will lose your job during such an event and therefore could not feasibly continue investing at the same pace (there goes DCA as risk-neutralizing strategy). The more likely occurrence in this scenario is that you actually NEED your invested cash to stay in illiquid assets (i.e. house, college tuition etc) and are forced to draw out money at the bottom of the market.

Index investing without any hedging for fat tails doesn't seem that smart.