Noticed this when slashing through the halls and dungeons on normal difficulty with my HC naked necromancer. It's best illustrated by images so have a look at the images below:
(RS = Raise Skeleton, SM = Skeleton Mastery)
RS 20, SM 12: Damage 89-91
RS 20, SM 13: Damage 101-103
RS 20, SM 13: Damage 94-96
RS 20, SM 14: Damage 106-108
RS 20, SM 14: Damage 98-100
RS 20, SM 15: Damage 110-113
The reduction in skeleton damage happens when I level up. The damage stays constant just untill I hit the next level, then the damage drops to the numbers above... ?!?!
To clarify: My RS is lvl 20, my SM is lvl 13 and my skellies deal 101-103 damage. Then I level up and before putting any points into ANYTHING the damage drops to 94-96 with the same stats, skills, etc. Btw I use no items, charms anything to influence the damage.
Anyone ever noticed this before or have an explanation?