Low allelic and clonal variability among endogenous RNA interference (RNAi) targets has focused mismatch tolerance studies to RNAi-active guide strands. However, the inherent genomic instability of RNA viruses such as hepatitis C virus (HCV) gives rise to quasi-species mutants within discrete clones: this facilitates mismatch tolerance studies from a target perspective. We recently quantified the slicing imprecision of Argonaute 2 using small interfering RNA (siRNA) analogues of the DNA-directed RNAi drug TT-034 and next generation sequencing of 5’ RNA Ligase-Mediated Rapid Amplification of cDNA Ends (RACE-SEQ). Here, we present an open source, customizable, and computationally light RACE-SEQ bioinformatic pipeline, describing adaptations that semi-quantitatively report the impact of RNAi hybridisation site mismatches from the target perspective. The analysis shows Argonaute 2 has a substitution-specific, 3-5 log activity window between fully complementary targets and targets with mismatches across positions 10-11. It further focuses the endonucleotic Slicer imprecision around positions 13-17, demonstrating its dependence on guide strand central region complementarity, and potentiation by even a single mismatch. We further propose pharmacogenomics value in testing endogenous targets using recombinant replicon systems and RACE-SEQ to report the pharmacodynamics of sequence-specific oligonucleotide therapeutics against all possible polymorphisms in a population, in a minimally-biased, patient-free manner.