Agreed. I enjoy the idea of the progression through the tiers. Offers great content. The saddle for the dragon took 41+ game hours. Only to find chieftains, skelies, Apex and others are immue to ranged attacks. (this Includes breath weapons from the dragon and Broodmother.) Forcing melee mechanics? Thats cheap and lazy. The dragon has the worst melee position. Everything gets below it or behind it struggling to make contact. About the only boss I've tamed that was worth while, the gorilla. Even then, way underpowered when all those I listed immuned to ranged attacks take reduced damage. So far, this mod is not worth playing outside the original game.

Bred Dodorex? Extinction Bosses cannot made, do you run another mod with it?
A-Giga is strong, but first you have to find a good one and own the saddle. Bosses are not to weak, but they are only for late mid-game / early end-game. Reach the final content and get Primordials and supremes!
Melee mechanics are cheap? I think ranged battle is what you can really call cheap. Luring strong encounters to an edge were they can't reach you and kill them by using the ranged attack from a lightning wyvern or something like that - that's what most people do if ranged attacks work.
The dragon has the abillity to fly - also backwards, what is a great advantage to kill creatures from air and avoid contact with minions on the ground, so it's ok that he does less damage.
To kill apex' or tek' use primordials or higher tier and it should be way more easy.
Sure, Extinction has lots of creatures and mechanics, and needs a lot of time with frustrating moments, but it's mostly very well balanced - that's the difference between EC and other core mods in the workshop were you can mostly easy rush trough in a few hours by using tricks and cheap mechanics.

And at the end:
It has ben said multiple times that Extinction core is made for max wild level 120-150. So if you play with max. 225 it's your problem that some fights seem to be imbalanced.