FSC was made extremely easy except for a few rooms were acceptable in how difficult they were for end game.
OCH is too easy as well as simple, in fact just plain annoying because of mortars (as in annoying, mortars not difficult at all just terribly annoying).
Shadow Lairs are a good difficulty while solo and great if OOO would allow it to be progressions based content, but shadow keys are ridiculous, I play this game to have fun and because I do not have to farm. Farming 1800 CE is not fun period and not worth it, as well as a total lie that this game doesn't require farming. Also, I shouldn't have to pay OOO $2.50 per solo shadow lair attempt (It is freaking 2.50 per attempt, do the math with buying CE with $$ if you don't believe me). Also solo because it is fairly easy to do a SL in a group. I also should not have to wait for a freaking - shadow lair key cost promo before I can have fun in this game and farm just a little bit less.
Devs please make the next expansion mission tough. We have a too damn easy one, make the next one require progression- as in I can't just go for my first time and kill everything, and I do not have to be forced to succeed because of a shadow key cost.
They won't ever add challenging content that isn't them trying to leech money off of us like shadow keys and I know it, but at least you can rage on the forums.
Note that this is NOT A SUGGESTION. It is to spark discussion about stuff, I hate the suggestion forums because they are worth nothing to the devs.
They are a a company, not a charity. They gotta do stuff like this. Some of their actions are debatable, but in general, their goal, like all other companies', is to make a profit.