As the title suggests I found that humanoid monsters which use weapons and execute styles deal significantly more damage than any other monster of the same level.
This goes across all levels, but is especially significant on low level where some monsters hit for 1/4 of a players life + apply a bleeding effect. While humanoids with styles make for excellent pets, they seem inherently unbalanced and too powerful compared to other monsters.
Monsters that wreck leveling solo players because of way too high damage: