The sad thing is that all they needed to do to stop the problem was to add the word "tapped" to the end of the last ability. Then it would be a sweet combo with Amulet of Vigor and Animate Dead instead of an annoying combo with just the latter.

The thing is, it would still be an infinite "I win" combo with anything down to a Sparkmage Apprentice.

That's why the easiest fix to Dragon would have been to say "When Worldgorger Dragon comes into play, if you played it from your hand, blah blah blah." Granted, it would have made the creature a lot more desirable to reanimate or cheat it into play, but that fix is guaranteed to prevent any of the infinite loops.