Challenging, yes, but far from impossible.
Most rooms can be trivialized by sniping from the platform with arrows and/or bomb arrows. Having all the quiver and bomb bag upgrades helps.
The darknuts move incredibly slow so as long as you keep them all in front of you their attacks are quite dodgeable. Just take your time and be prepared to react accordingly. Hidden Skills (best ones probably being the helm splitter and mortal draw) work wonders against Darknuts.
If you need hearts, come with a few fairies. Additionally, one of the floors has a rare chuchu (the sparkling gold one) which drops a chu jelly that fully replenishes your health and gives you double damage until you get hit. Some of the floors, notably the ones with poes and invisible rats, have dig spots in which you can find hearts as well.
The spear throwers (known as Chillfos) are pushovers if you use the ball and chain. Bomb arrows are also quite effective against them, or if you wish to save arrows then Bomblings are a hidden gem that are fun to use and can be useful when dealing with enemies like that. Ball and chain is my preferred weapon though because it also acts as something of a shield while you're holding it.
If you're still struggling, then I suggest seeking out all or most of the hidden pieces of heart (the fortune teller in Castle Town can help with this); and, for even more protection, find all the Golden bugs to fully upgrade your wallet and complete the Malo Mart side quest to purchase the Magic Armour. With a fully upgraded wallet, you can get through most of the floors without taking any damage.
Just keep at it. Follow the advice given by myself and others in this thread and you'll get through it, no cheats required. I've done the Cave of Ordeals as part of a three-heart challenge so it is absolutely doable! Good luck!