here are the some ways they can be dealt with
1. Steal lobo and take out momentum ability
2. Mutate your own creatures to get abilities to stop the dragons, like freeze and mutate
3. Try to save your sundials as long as possible, for when there are momentum dragons
4. Mutate the dragons, with fallen druid it still works pretty well. It helps to get your otyugh's as big as possible before mutating, so it's more likely they can devour the mutant (sometimes devouring your own creatures is worth it)... rain of fire can do 3 more dmg to whatever you mutate also.
5. Destroy the grav pillars to slow gemini down, after a certain point gemini will use parallel universe on your much weaker creatures, like a 4/9 otyugh or a firefly queen.