Increasing damage and hp of the monsters is only a quick fix which fails to tackle the real issue, IMO.
At higher lvs, it isn't damage which wins fights. It is battlefield control spells which shut down all the foes altogether, giving the fighter free reign to whack them to his heart's content.
So if a monster is simply going to be standing there impotently, it doesn't really matter if it has 1 or 1 million hp, or if it deals 1 or 1000 damage per hit, does it?
And the players will likely quickly adjust their tactics to work around your so-called fix. For instance, if I know my foe will have so much hp that damage is ineffective, then I would probably switch to save-or-die effects, or maybe find some way of skipping the fight altogether (like forcecaging him and continuing on).
What are you going to do then? Make the monster immune to every effect in the game?
I won't say it is necessarily wrong, just that it comes across as being very inelegant. Seeing that your players are clearly fine with what you are doing, I don't think I am really in a position to complain or protest.
However, one issue I have with this is that it doesn't seem to reward the players for being strong. It is more like punishing them.
"Oh, you deal twice as much damage as a typical fighter? Congratulations, now every monster automatically has 10 times as much hp thanks to you."
If you look in the 3e forum here, there were a series of threads started by a member named jeffct who sought a lot of advice on creating high-lv encounters to properly challenge his party. It took a lot of work, since he preferred to stick with the existing rules, and classed npcs are notoriously weak/fragile for their crs at higher lvs. But he managed to pull it off.
I think what the OP might need to start to do is to learn to use more challenging tactics, rather than just inflating the stats of his monsters.
At higher lvs, it isn't damage which wins fights. It is battlefield control spells which shut down all the foes altogether, giving the fighter free reign to whack them to his heart's content.
So if a monster is simply going to be standing there impotently, it doesn't really matter if it has 1 or 1 million hp, or if it deals 1 or 1000 damage per hit, does it?
And the players will likely quickly adjust their tactics to work around your so-called fix. For instance, if I know my foe will have so much hp that damage is ineffective, then I would probably switch to save-or-die effects, or maybe find some way of skipping the fight altogether (like forcecaging him and continuing on).
What are you going to do then? Make the monster immune to every effect in the game?
I can understand how some of my reasoning feels counter-intuitive or strange. I am not the best writer, so sometimes I leave out important notes. But my methods of dealing with the situation have worked well for me (honestly, I don't have a group full of people who think I cheat, or who feel 'bullied' by me), and I just wanted to share those with everyone. Which is, after all, what forums like these are for.
I won't say it is necessarily wrong, just that it comes across as being very inelegant. Seeing that your players are clearly fine with what you are doing, I don't think I am really in a position to complain or protest.
However, one issue I have with this is that it doesn't seem to reward the players for being strong. It is more like punishing them.
"Oh, you deal twice as much damage as a typical fighter? Congratulations, now every monster automatically has 10 times as much hp thanks to you."

If you look in the 3e forum here, there were a series of threads started by a member named jeffct who sought a lot of advice on creating high-lv encounters to properly challenge his party. It took a lot of work, since he preferred to stick with the existing rules, and classed npcs are notoriously weak/fragile for their crs at higher lvs. But he managed to pull it off.
I think what the OP might need to start to do is to learn to use more challenging tactics, rather than just inflating the stats of his monsters.