A large chunk of the mages was assembled away from the fight, and it was where the Thunder King landed with one leap. The moment when the aggro shifted away from the Tanks happened so fast that the ranged classes didn't have time to evade.
No one expected that Ivan, their veteran commander, would make such a slip. It had never happened before, and they had a hundred percent faith in him, so everyone's guards were down. Now, they suffered the consequences.
To begin with, Mages weren't fast, unlike the melee units. Some of them were in the middle of casting a spell, too busy to even notice the approaching giant, while those who did notice thought that it would target the Tanks.
A few were lucky enough to survive, all of which who had excellent map awareness and level-headed gamer minds. Unfortunately, Ivan was so shocked by his blunder that he couldn't [Teleport] on time. He died with eyes wide open and a heart full of frustration and regret.
There was no way that they could acquire one with their current level, especially since adult Dragon Birdbeaks were like mini-bosses, and they're often aggressive and territorial, attacking in groups to protect their eggs and children.
Sometimes, developers would randomly auction rare items in the COVENANT auction house. That should explain the rare items that the rich guilds and players own besides them buying in the Black Market; otherwise, they couldn't be acquired easily this early in the game.