Don't use a rocket to deal the final blow because the body will fly off the side of the map and you won't be able to get the element

Don't believe the other people. They are all talking about the wyverns.
The actual boss dragon is tough to defeat on hard difficulty.

The dragon is untamable. Period. You’re welcome.

To kill the Dragon, bring a decent amount of 100% inprint Rex’s (maybe around 10-20) a few friends, rocket launchers and guns and you will hammer the dragon or any other boss

This boss is like a trike,it will not attack nor notice you only if you attack it. If you plan on forcetaming it there's a bug it will disappear after a while!