The castrum has the difficulty of a alliance raid.
It can be done when you have 2-3 better prepared player who knows what to do.

But the rewards in there is....
The amount of medals needed for the glam armour is fine, in a few runs you got the set you want.
But to need 1k medals to upgrade haste on one single part is just way to much....
You get 25 medals per run and need thousands to get gear that helps you in the instance with more haste is just not worth the time.