Here's what I would have done to make them near perfect
1. More variety
2. Make them more rare
3. More powerful
4. Different battle tactics
I agree on variety, They really need more variety than they have. At least have diferent markings, colours, forms.
Don't make them more rare, they're awesome, rare svcks! Make more dragons instead.

I agree on more powerful. They are too weak, sometimes.
The battle tactics, well theres only so many you can put in. But yes, they could be more varied.
They need more than fire and ice breath. Plasma, acid, darkness, electricity, force, theres lots of elements they could be. Mixed ones, like, Acid Ice, Electric Fire.