For a while now the Pimpernel and Lyuda have been accepted as the best snipers for mobbing and raiding respectively. However, the Amigo Sincero is incredible vs enemies with big shields and has immense one shot, one kill potential vs mobs due to base damage.
If Man of Low Moral Fiber is still around, please review the Hot Mama and Amigo sniper rifles man, and hope you will be sniping and posting vids in BL3 