That SA and TA affecting all hits would be epic. Maybe not giving the DEX and AGI boosts for each hit, that would be hideously overpowered on a 30sec~ish recast lol.
But Having the innitial boost recieve the DEX or AGI boost and then having every other attack in that attack round (including additional hits on WSs) being automatic criticals would be awesome. That would be an awesome damage boost. Like you say, a high level trait, like: [NAME] Lv. 95. Garantees any addtional attacks to be critical hits under the effect of Sneak Attack or Trick Attack.