Actually we can put in 20 points into the final trait, which at a rate of .75% stamina per point, gives us a total of 15% more stamina.
In other words, 54 traits equals 54*0,75 = 40,5% more stamina.
However, once 7.2 hits live, we'll get 39 points if we currently have our artifact maxed out. 39*0,75 = 29,25% plus the 10% increase from the new "trait" giving our weapon the same strength as before, gives us a grand total of 39,25% stamina.
Just curious.