Alrighty. Just give a shout and I will see about dropping some advice.
As far as nightmare mods go, they aren’t really…beastly. Most of them are pretty fun, but some aren’t all useful (though, yes, some are quite powerful). Also, the missions themselves often have frames or weapons that offer a counter to the negative effect and make them trivial.
No shield mode? Use Inaros, he had none to begin with and is still a beast of a tank. Same with Vampire mode, though Nidus and Oberon work well there, too.