I have a different build that kind of avoids the problem, although I don't like it quite as much from an RP perspective:
Elven Bounty Hunter
Race: Elf. Align: True Neutral
Str 12, Dex 20, Con 12, Int 12, Wis 8, Cha 8
Rogue 1 - Pointblank Shot Rogue 2 Rogue 3 - Weapon Focus Longbow Rogue 4 - Dex to 21 Rogue 5 Rogue 6 - Rapid Shot Rogue 7 Rogue 8 - Dex to 22 Bard 1 - Toughness Arcane Archer 1 Arcane Archer 2 Arcane Archer 3 - Dex to 23, Imp. Critical Longbow Arcane Archer 4 Arcane Archer 5 Arcane Archer 6 - Dodge Arcane Archer 7 - Dex to 24 Arcane Archer 8 Arcane Archer 9 - Open Feat Arcane Archer 10 Rogue 9 - Dex to 25 Arcane Archer 11 - Great Dex I (26) Arcane Archer 12 Arcane Archer 13 Arcane Archer 14 - Dex to 27, Great Dex II, III (29) Arcane Archer 15 Arcane Archer 16 Arcane Archer 17 - Great Dex IV (30) Rogue 10 - Dex to 31, Improved Evasion Arcane Archer 18 - Great Dex V (32) Rogue 11 - Defensive Roll Arcane Archer 19 Arcane Archer 20 - Dex to 33 Rogue 12 - Epic Dodge Arcane Archer 21 Arcane Archer 22 - Great Dex VI (34) Rogue 13 - Dex to 35, Self Concealment I, II Arcane Archer 23 Arcane Archer 24 Arcane Archer 25 - Self Concealment III Arcane Archer 26 - Dex to 36, Epic Focus Longbow
So we wind up with Arcane Archer 26/Rogue 13/Bard 1.
I hate single levels of classes taken to satisfy requirements, which is why I think this RP's less well, but what can you do?
This build doesn't have to waste 3 pts on Charisma (I hope) because it starts with Rogue and not Bard. So it gets all-around better stats for a sneaky archer.
Attack winds up at +54 instead of +56, due to 4 less overall Dex. However the Sneak Attacks are now 7d6 instead of 5d6 and do not have the chance to Paralyze. I think the offense is down a bit in this build, but not ciritically so.
Defensively the build is much stronger, trading off 2 AC from lower Dex bonus for Epic Dodge, Improved Evasion, Defensive Roll and Self Concealment III (30% chance to completely avoid any hit!)
Skills wise the build has +48 skill pts from taking 13 Rogue levels instead of 8 Assassin and 4 Bard. This makes the tradeoff for Darkness, Improved Invisibility and the Bard spells into basically a fully optimized skill of your choice. I think the Drow Hunter Assassin gets the better of the deal here but not dramatically so.
I'm going to throw this one together tonight and see how it feels.