Dumping zec as soon as you mined it doesn't make any sense to me either.  The availability of zec is still under 2k. When zec went live there was less than 3 coins on the market therefore driving the demand up to 5k. Limited supply, high demand = decent price. There is no reason for the price to plummet this far.

 I believe the same concept still applies. There is still a limited amount of zec coin available to be mined by miners and to be traded on the market. If you dump your zec coins for cheap then you are just shooting yourself in the foot. You would be mining a coin that is drastically losing vaule. I don't think everyone who is mining zec understand that it will not make them millions or even thousands of dollars if they continue to mine and dump. There is just not enough supply at this stage of "slow low block payment" of zec.

Everyone is free to make their own decision. They can mine and dump. It's a free country!

However, I will caution that if we, as miners don't hold on the price of zec, we will drive it to the ground before we can even get 13.5 zec per block chain. We will all jump back on the ETH boat because it will be the most profitable coin to mine, driving the diff bomb back to 100t plus. Then what? What happens when ETH goes POS. Which coins will we chase next?