"Newcomer-2011. Winter"

Well, actually, the Hive's birds when building the Mighty Gorgon in the Castle is 3+7+7+9=26 birds
it's unclear where the 15 Dendroids came from in the native army :)
in the third version, such a creep will have all the shooter burned for sure, only Thunderbirds and Mighty Gorgons will remain) and also I have vague doubts about Mighty Gorgons in the Castle as a standard, you might be able to build it, but how to quickly buy them all on week 1 day 2 and transport all the folders to the treasure zone is a very interesting question :)

generally, to take a Dragon Utopia, you need to fulfill 2 simple conditions
-having a striking stack with 700+ damage
-having a shooter that can withstand at least 3 rounds

of course Mass Shield and Stone Skin greatly simplify the task, there is a subtle point here: to cast spells before the Greens and Reds' turn, it's highly desirable to have someone with speed 11+ (even a single one!)
also an interesting observation:
- if on the 1st turn our stack of Angels (or say Monks) hits the Greens or Reds, then both of them will target precisely it in the same round
- casting Shield or Stone Skin on a unit sharply increases the chance that it won't be touched
- Dragons are terribly fond of pecking Nagas, Hydras, Crusaders, and Dendroids (the conclusions in each specific situation are your own :))
and the classic way to take a Dragon Utopia with 7 single units, regardless of which ones, and a hero with Spell Power 10+ and Summon Elementals — when 1 Green remains, if there's no Expert Recurrence, we simply retreat and finish off the unfortunate dragon with a scout hero :)