A level 13 thief can easily achieve a +25 vs AC attack (+5 Dex, +6 level, +3 prof, +3 enh, +2 expertise, +1 Talent, +2 CA, +3 backstab) that deals 6d6+17 (1d6 shortsword + 2d6 SA + 3d6 backstab + 3 finesse + 5 Dex + 3 enh + 2 expertise + 4 acrobat's trick) on a hit. That attack bonus should hit...