I'm a bit split on what that creature's CR was. It has below average hit points, but above average AC along with DR, elemental resistance and flight speed, so its defences are pretty good. In the offense department it has its breath weapon which is pretty good and death throes add another opportunity to lose HP. Its attacks are less spectacular as they are not that accurate, and whilst it has 4, none of them deal that much damage, but one of them does deal dex damage. It also has enough ranks in stealth and hide to have a pretty good chance of catching PCs unaware.<br/><br/>Overall I think I can't decide it it’s just high end CR 6 or CR 7. I did make some changes, such as cutting the DR in half and adding a cool down time to the breath weapon and I also gave it a minor debuff. There is also the fact that the logical tactic for the creature, flyby attack with sting repeatedly, is very hard to deal with online. In the end I treated it as a CR: 6 creature but gave you an extra 100XP since it was above average.