It may seem like a no brainer, but I don't always go by the book in regards to how much HP I give the monsters. The casual battles should only take so long so I think of how many rounds I want them to last and I average my player's attacks. Then I just multiply or scale it to how long I want the fight to last. The bosses should last around 10 rounds or so. That choice is yours. But I do the same thing. Now I average it out with the notion that some times they may roll low. If they roll high or get a crit, good for them. However, when faced with this "bloat" of HP, I make the enemies as powerful as the PC's for this reason. Whatever the players can have, so may the enemies. It's your story and shape it the way you want. So my player may have some sword he took from a late billy-bad-ass McGee, I start to equip the skeletons more powerful attacks bestowed upon a more powerful sorceress or necromancer to only showcase the power they are going to face. I have even went as for to enforce "Mega DMG" from Rifts to give an Elden Ring vibe, so don't be scared to try a X10 or X100. Some things they learned through "naughty word around and find out" that you just don't mess naughty word or jump head in like you're indestructible. Some things are not meant to be fought. Just survive. The fact that I keep them on their toes and nearly have them die every night and still return, I must be doing something right. I have even added sand warms from Dune that would take them under the ground and gave them 3 chances to roll before suffocating. It was never about the rolls. Its about the since of danger. I was never going to kill them, but I would have them pop back out at the last second. Monsters swallow players, nearly get cut in half by pincers, mysterious illnesses, etc. I've even thrown heat at them and made them realize their armour was only an oven at this point. When you make them realize that they can't always rely on what gave them their edge, you make them question are they actually safe...The adventure seems like so much more. Take the squishy safety from them and impliment the dangers they once knew and loved. I'm 37 now and been playing for 30 yrs. I started with my father and Uncles who had us play with just an index card of our 6 stats and modifiers and flew by the seat of our pants. I have carried the tradition after my father passed and kept the charm of life is something not to take for granted and keep mystery around the corner.
I guess what I'm trying to say is, don't let this discourage you. It's an avenue for you try something new. Develop new things for them and bring back the since of danger. And remember, there are more frightening things than death.
