It seemed the more squishy my characters were, the better they were at handling the more difficult mobs. My blaster was more of a kill them before they kill me type of character, with ice patch and sleet to buy me some time, as well as a couple of holds. Useful for arachnos, as long as I had used Clarion or had a break free.
My brutes, scrappers and tanks just didn't seem to fare as well, presumably because of the higher difficulty settings. But, those arachnos seemed to just eat through my defenses pretty easily. If I hadn't had a macro for popping purples, my poor brute would probably be face down in a warehouse somewhere.
Overall - my least favorite was longbow - because I'd try to find an anchor for my kin, and somehow, I'd end up with a singularity and waste the opportunity.