In 3.0 OA, the tattooed monk gained DR 2/+Con mod. That means my 20 Con half-ogre has DR 2/+5. (Plus I took the feat, Thick Skinned from SS, to make it DR 4/+5.) This is far superior to DR 2/magic.
Also, the reroll tattoo in OA is one reroll per tattoo. In 3.5, it's one reroll total.
This is...