I started after H&H and only play solo. I don't know just how easy it was before, but I have had no real problems going through the current content (up to killing Yag) three times. The last time I started just before the Abominations were introduced, so they were there when I got to the swamps. When I have been mobbed on I realized what I had been doing, and modified my behavior.

Whenever I read a post about mobs being too tough and being ganged up on, I believe its just moving too fast through a new threat area and pulling too many mobs to handle. They probably could deal with things if they just took a bit more time exploring and just step back when they advance on your position, instead of running toward the new mob thereby pulling more to themselves.