All classes complain about there shortcomings, but when you analyse it, its not that big a problem. So instead concentrate on adding some variety to the classes. Here a suggestion for the engineer that could be usefull with the coming camps.
An Engineer made cannon
You see them at the outposts already, but who built them? An Engineer of course.
I suggest that an engineer would be able to build stationary cannons that could do area damage (like NT spell).
This would be usefull in teams, as it would probably have to be instead of a pet to keep the balance.
Again the Arts is in there, now make it usefull!