Quote Originally Posted by ARTHAN View Post

I used to use MM1 monsters most of the time but I also included MM2 monsters as well as monsters from other books (MM3 is one of them but I am not 100% sure). Before I stopped playing for real-life reasons, I was mostly making homebrew monsters by relying to DM's Guide 1 and 2 guidelines as well as my own experience. Unfortunately, I came up with this rule at the end of my DM career and not earlier. :(
This is a big part of your problem. MM1 and 2 used bad math, and that’s true of DMG1 (and I believe 2) as well. MM3, Monster Vault 1 and 2, adventures and splatbooks printed post MM3, and to some degree Dark Sun use the proper math, which reduces monster defenses in some cases and increases damage. Most of the MM1 and 2 monsters were reprinted in MV1 or elsewhere with the correct math.

The correct math can be found here: https://slyflourish.com/master_dm_sheet.pdf and here http://blogofholding.com/wp-content/...inessfront.gif.