The dragon is hard even on easy if you don't know what to do.
As @Gromuhl said it's possible to not burn to a crisp.
Basically stay under the wooden structure, look up onto the dragon and when you see it stop breathing, proceed to the next. Repeat again.
As for Dark Mode. Well Normal was hard until the first few hours but after that I aced everything. Though Gargoyles are despicable, if you let them group on on you, than you're dead.
I'm dissappointed by dark mode personally, because the only difference I see between that and normal is that you get hit harder. (and the dark sets make seeing enemies a bit harder with that black fog) You die very easily until you get a nice set of armor and put points in the perk that reduces damage from attacks to your back.