Besides the aforementioned tactics, you should also use the "kiting" strategy, i.e., attacking a dragon in such a way that the retaliatory attack hits another dragon.
However, the situation with hydras is not so clear-cut. I prefer to use a single-unit in a corner. In this regard, wamp lords, ogre lords, and even golems are quite good in a pinch.

Орден Феникса – харизматический :) лидер