Some of the fights is going to require a bit more.
Golem one you need to kill off the bomb adds that spawn in 2 waves before they start moving towards you.
Cyclops one you will get 2 waves of puk adds that needs to be dealt with else their little damage will add up.
These 2 are what people consider the harder ones...

Some other tricky ones are
Malboro - it will bind you and use bad breath. If you are a healer, you just remove the bind, if not, you stun/silence/sleep the bad breath.
Bombast - unless you are overgeared, don't attack it when it turns big

There are more maps, you just have to learn them one by one. If you don't feel confident, bring a friend.