It would absolutely be viable in honour mode. I'm currently playing around with it in one of my own runs. For leveling I think, however, going warlock 5 -> fighter 3 -> rogue 4 would be a better leveling path, with potentially a respec involved to get 2 feats while level 9-11. Eldritch blast is a good alternative turn use in act 1 until you can pick up a +2 rapier, and infernal rapier can be a filler until you can fully exploit Duellist's Prerogative and multiple bonus actions at level 12/early Act 3, which is when piercing damage becomes king anyway.

@@friederichh6543 If you don't mind switching the helmet out I think the DIADEM OF ARCANE SYNERGY could work incredibly well, lower crit chance but adds your spellcasting modifier as damage which I believe is defaulted to the weapon damage, piercing, and Bhaalist armour inflicts a condition. I have not tested this but could theoretically double your charisma bonus to damage?

@@hoodedalpha4880 Absolutely, but I think you would abandon crit fishing entirely as a strategy if you go that route, drop risky ring, get one of the haste bows instead of deadshot, etc. Core of the build is piercing vulnerability/DP/riposte/sentinel/Pact of the Blade Warlock for added utility. Crit (synergizes with GOO warlock) v. Arcane Synergy (less GOO synergy, so open to other warlock subclasses) are both good variants.