I've been at it for over 2 days! Level 15 Diamond usually does well.. forget it. Level 15 Champion.. forget it. Tried some other Level 15 dragons but I really can't heal them fast enough! I've beaten this guy often in the past.. this one is getting on my nerves! lol!
Here’s what works for me, heal the one you use from the calculator, that will be diamond for me, it usually works 2nd time around. This works with many of the problematic ones, this means, you need two hours. I know how difficult it is to try and use another one on list, but, most definitely, my healed dragons beat the opponent all the time, berserker was finally taken down with Diamond for me.
My Diamond usually work great on this one. Not this time unfortunately. I would have been happy with 4 goes at him. I just got beat again! It's become humorous now. lol! Not having the greatest luck this month with breeding either. That's what makes the game fun I guess. Good luck.