The end stone is mineable, BUT you need to get out of the end alive with the materials, if you die in the end then all your items drop.. Although defeating the ender dragon isn't that great a challenge if you come prepared. I agree with what yoursaying, to add challenge to finding the end, it should only be enabled in Resource Zone. Also, I believe that the end portals are open 1 hour every 2 weeks, however you can open the end by force if you throw a dragon egg into the portal!
