As much as I like cute squirrels - no, Pachirisu should not be used (not competitively outside of NU anyway).
Additionally, Gen IV saw Pachirisu have 2 useless abilities in Pick Up and Run Away. At least Gen V gave it Volt Absorb.
Conclusion: Pachirisu has a shallow movepool, mediocre stats and bland typing. Not worth using.
In game - Pachirisu can prove itself useful with Pick Up, but not so much in battle.