So it appears that either True Shot was ninja-buffed at some point or Ranger gets a second tier of the trait by level 90. When I first got it and tested it, it was clearly a 3% damage buff, but a while ago I noticed my damage on capped targets was consistently higher than possible with only a 3% buff.
So, I first checked in La Theine with a Vision Bow/Demon Arrows total damage + capped FSTR2 of 167
Hit from melee range = 501 as expected (167 * 3)
Hit from the sweet spot = 536 (this was with AF3+1 legs on)
536 / 501 = ~1.069
I checked it again yesterday while I was testing Dead Aim in Ronfaure.
Short Bow +1/Wooden Arrow total 27 damage (this time naked so no AF3+1 legs)
Hit from melee range = 81 (27 * 3)
Hit from sweet spot = 85
85 / 81 = ~1.049
So it appears at level 90 at least, Rangers now get a base True Shot bonus of 5% and the AF3+1 legs add 2% to that for a total of 7%.
If someone could check on COR or a lower level RNG it would be appreciated to know whether it is indeed a new tier of True Shot or whether True Shot was ninja-buffed.