Oh the Spider Queen. I reckon you didn't read my comment on Steam about the Ice Hydra yet... I can definitely relate.
The interesting thing in this game is that at higher levels resistances and damage types are much more important than they are made to be at the starting point. You should catch a video of user Hooyaah going against the Ice Lord with an Ice HE and you'll notice that even with hundreds of points in the skills it's hard to cause it damage because it's ice vs ice. And a Pyro HE is kind of limited to fire+physical so when a tough opponent is resistant to those you're in for trouble, and you either have a huge amount of DPS or you're screwed. Try killing the Forest Guardian on Dryad Island, it keeps casting full heal over and over again, and unless you can get its HP down fast enough you really can't kill it. That boss has been my go-to test for checking if my DPS is good or bad, if you can kill it it's good. But I agree that many mini-bosses are actually harder than the campaign bosses. Narnuil, Abishai, Ice Hydra, Forest Guardian, Spider Queen, and probably more that I don't have at the tip of my tongue are all very hard. Get frozen by Narnuil once and say good night. Drop the ball and let yourself be caught by the Abishai's traps and bye bye. Face any of the remaining three with a lower than godly DPS and it's sayonara baby.
But then again, that's more to do with the actual game design that with CM Patch. Opinions may differ but I for one don't think the CM Patch is to blame for your death.
PS: Do you happen to have Ancient Magic? Having it mastered should really help you cause more damage, even taking resistances into account. That skill breaks resistances on top of boosting spell damage.