Cross-server Boss has been relatively weak recently, since the evening version scaled down by a large amount. Maybe you’ve just been unlucky with rooms. Since it’s meant as a cross-server event, having it be based on servers would be contrary to the point.
There have been frequent complaints about the Ancient Catacombs Dragon, and those are possibly justified. However, there are stronger variants of the map dragons, the enchanted dragons available from ult. 8 onwards. Further, the dragons have been bugged and producing a much stronger variant after each maintenance. Making them stronger by default would be punishing to earlier servers where they still take a while to kill, while having them scale would be slightly redundant given that the enchanted dragons are already stronger dragon variants that scale. The enchanted dragons already take a long time for people to kill, typically, so having the normal dragons last for long would be unnecessarily tedious. Besides, people in this game can grow unnaturally large quite quickly, and several variants have players of around 400M+ BR. To make the dragons last long for such players, they’d often have to become almost impossible for others to kill at a decent rate.