Ryujin
Legend
I've got a tattoo that lets me teleport when I get critted. Its so-so but it has saved my butt once. Our cleric has Prophecy of Doom (PoD) which lets you turn a hit into a crit. Our cleric won init, planted PoD on our target, but there was one bad guy who went right before me. He nailed me and weakened me. Thanks to the tattoo I teleported and ended beside my Paladin buddy. I delayed to go after him, he touched me and removed weakened and then I critted the bad guy for 117 damage. That was fun!
One other thing I will point out for the Shadow Warlock Armor. Keep in mind that with cursegrind and cursebite, thats a +2 against every target, not just one because they are all cursed. That significantly ups the to-hit chance and makes those powers even more significant than they already are.
My guy is mostly a stay in the shadows kind of guy. He's big on intimidate, bluff and stealth when needed so the armor fits quite nicely.
To b e honest, I'm surprised that people haven't complained about the magical tattoos. They exist in a newly created item slot. They can have some rather powerful, though admittedly situational effects.