They are actually pretty darn similar, though Helms' tattoo is a bit different -- a little squarer.
My gut feeling is that the lawsuit doesn't have merit, though I have difficulty putting together a legal justification of why that is. My general feeling is that the actual tattoo design is too generic a combination of random Maori design elements to be copyrightable.
But no, I don't think this is a publicity stunt by Warner Bros. But yes, clearly it is a money grab by the tattooist.
The whole thing smells of publicity stunt by Warner Bros, and a money grab by the tattooist.