The SR for tattooed monk caps out at 25, and the Crescent Moon Tattoo only has 1 use as compared to Empty Body which has 2.
Tattooed Monk is an interesting sidegrade, but not better.
Many monk class features need to be taken intentionally with the class and to lesser effect than full monk.
The buffing is cool and everything, but overall lacking, with the most interesting tattoos being mountain and crab.
Everything else is easily done with consumables, but of course having them innately is nice and of course I'm sure they stack with traditional buffs.
That being said, it is an amazing way to add flavor to the class's usual archetype and it does have plenty of interesting options and avenues.
(I think that regular monks should get access to the ocean tattoo's benefits at level 15 regardless, but that's just for fun.)
Though the KD immunity is nice as is the crab tattoo DR, that's a lot of what it has going for it.
It also comes online later than regular monk for strengths that aren't really worth the cost of losing the base monk class features later on.
A good few of the buffs are lackluster and only really a handful are worth taking unless you're looking for the RP flavor, which is nice to have as an option.
I think with the PRC coming though, regardless of it's strengths, does somewhat fix the problem of going level 20 for high level monks should they wish to pursue it to not incur that OCR increase.
I feel like there should be a light padding of the base class capstone at 20 to make taking the level more incentivized for those that do want to stick on the path all the way along. Ki Strike +4 comes to mind mostly, though upping the perfect self DR to 20/+2 would also likely be just as good considering what can be achieved with the mentioned Crab Tattoo now.