When many go dragons, I have success with faceless 4-cost

Doesn't do anything about the magic ressistance though.....

It is OP ♥♥♥♥♥♥♥♥ and easy way to top 3 but thay are basicly fast bursting mages, you need to counter mages not dragons. Usualy in the late game i sacrifice a synergy to get 4 nagas (lets say get out of 6 beasts to 4 or get out of 9 warriors to 6 warriors). Then add disablers like Tide or Disruptor and put Refresher on them. Also, 4 Centaurs with Magnus stun destroy mages-dragons timings couse all they have is basicly one huge damage burst that comes faster then your units can do damage. Stop that or dealy it and they get obliterated. Dont try to do huge damage you dont need it. Disable them and silence them and they will die to half the damage you think you need.
You will see one round they will give you 20+ damage and the second you make some of this changes you will do 20+ damage to them and game will be over in 3 rounds couse they can not adjust their build like you can.