I didnt remember having so much difficult with other dragons, but maybe it's just that I started playing the expansion after several months I finished the game, but again I think that at normal a better balancing would be better.
The fights should have a much slower pace, oneshots and absurd levels of resistence and immunities are not fun (well not for me). Usually a "use paralize" spell/scroll -- resist ---all dead --- reload mechanic is very bad in my opinion.