The new Hearthstone curse bosses aren't all that hard at the moment. I got the first and third one on the first try.
You just have to be smart about how you trade around your stuff, though the second one is just annoying.
The third one wasn't terrible, since I had a few cards that benefit from returning to the hand anyway.
I mostly just played around until I got a good card combination, then RECKLESS ROCKETEER + COLD BLOOD + COLD BLOOD, which while not creative, is still an effective finisher.
...one random damage for every card in your hand... meh. Spiders from the previous boss helped with that one.
The side challenges are cool, since they are basically puzzles on how to knock them out with a deck they give you.
The hardcore bosses are just cheap, though I can see how you might beat them. Well, I can see a metaphorical framework for the first one, anyway. I don't quite know how I would go about the execution at the moment.
I didn't have to adjust my deck all that much, but the prize cards are nifty. I would use some of those.