Level 40 is too low for Dragonspyre. You're going to be up against it.
I suggest that you go back and do the side quests in Mooshu, also Marleybone. The extra experience and added levels will make things easier.
I am level 38 and just got to Dragonspyre. But, I've completed the world 6 times, so I think I'll be okay. If you know what you're in for, and have experience, you should be fine. Someone called me a "noob" earlier today, but when I told them I have 5 legendary wizards, they tucked their tail between their legs, and went sulking away. If you want help, keep an eye out for me!
Molly, level 38 Life wizard and Moose, the wonder Minotaur :D