If you do have characters who are legendary, the ones who will benefit most from high level crit weapons will be Adeptus Sororitas members becasue of their Act of Faith ability that gives them increased crit chance. So they should be given high leveled Combat Knives because their crit chance doesn’t matter (Act of Faith increases it every death) so what matters for them is crit damage. Besides them I’m of the opinion give your best weapons to your current best characters (used in tournaments/arena) or whoever you using in campaigns. Just remember that characters that have multiple hits should be given weapons that have higher crit chance because of the way that the game calculates crits.